Magnetic recording and reproducing apparatus

ABSTRACT

A magnetic recording and reproducing apparatus wherein synchronizing separation of a reproduction video signal can be performed accurately and a stabilized reproduction video signal can be obtained. The magnetic recording and reproducing apparatus includes a switch device for selectively inserting, upon recording, a PCM modulated audio signal into a blanking period of an FM modulated video signal, a PCM region signal generator for identifying a region of a PCM modulated audio signal in a reproduction signal reproduced by a rotary head and generating a control signal representative of a PCM audio signal region, an FM demodulator for FM demodulating a reproduction signal from the rotary head into a reproduction FM demodulation signal, and a clip circuit for clipping a lower end portion of a PCM audio signal region of a reproduction FM demodulation signal from the FM demodulator in accordance with a control signal generated from the PCM region signal generator.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetic recording and reproducingapparatus, and more particularly to a magnetic recording and reproducingapparatus of the type wherein a video signal is FM (frequencymodulation) modulated and a digital audio signal (hereinafter referredto as PCM (pulse code modulation) audio signal) is time divisionmultiplexed into a blanking period of the FM video signal to produce arecording signal and then the recording signal is recorded onto andreproduced from a magnetic record medium by means of a rotary magnetichead.

2. Description of the Prior Art

Magnetic recording and reproducing apparatus are already known wherein aPCM audio signal is inserted into a blanking period of an FM videosignal to produce a recording signal and the thus produced recordingsignal is recorded onto and then reproduced from a magnetic recordmedium by means of a rotary head. An exemplary one of such conventionalmagnetic recording and reproducing apparatus is shown in FIG. 52.Referring to FIG. 52, the magnetic recording and reproducing apparatusshown is a video tape recorder and includes a recording system includinga pre-emphasis circuit 10 for emphasizing high frequency components of avideo signal, an FM modulator 11 for FM modulating a video signal, a PCMencoder 12 for processing an input audio signal by shuffling, additionof an error correction code and so forth and time base compressing thethus processed audio signal so as to allow an audio signal for one fieldperiod to be inserted into a vertical blanking period of an FM videosignal to PCM modulate the audio signal, a pair of changing overswitches 13 and 14 for alternatively selecting, upon recording, an FMmodulated video signal and a PCM modulated audio signal, an adder 15 foradding an FM modulated video signal and a PCM modulated audio signaloutputted from the changing over switches 13 and 14, respectively, arecording amplifier 16 for amplifying an output signal of the adder 15,and a recording video head 17 in the form of a rotary head for recordingan output signal of the recording amplifier 16 onto a magnetic recordmedium in the form of a magnetic tape 200.

The magnetic recording and reproducing system further includes areproducing system including a reproducing video head 18 in the form ofa rotary head, a reproduction amplifier 19 for amplifying an outputsignal of the reproducing video head 18, a PCM decoder 23 for decodingan output signal of the reproduction amplifier 19, that is, fordetecting a PCM audio signal inserted in a vertical blanking period of areproduction signal and processing the detected PCM audio signal byerror correction, de-shuffling and so forth to restore an original audiosignal, a reproduction equalizer 20 for compensating for a frequencycharacteristic of a reproduction FM video signal, an FM demodulator 21for FM demodulating a reproduction FM video signal, a de-emphasiscircuit 22 having a reverse characteristic to that of the pre-emphasiscircuit 10, a clamp circuit 24, an analog to digital (A/D) converter 25for converting a reproduction video signal from an analog signal into adigital signal, a synchronizing separator circuit 26 for separating asynchronizing signal from a reproduction video signal, a reproductionsignal processing circuit 27 for processing a reproduction signal bytime base correction, dropout compensation and so forth in accordancewith a synchronizing separation signal from the synchronizing separatorcircuit 26, and a digital to analog (D/A) converter 28.

The magnetic recording and reproducing apparatus operates in thefollowing manner. Referring also to FIG. 53 at the top of which a videotape is diagrammatically shown on which a recording signal in which aPCM audio signal is inserted in a vertical blanking period of a videosignal is recorded, an video signal inputted, upon recording, to therecording system by way of a video signal input terminal 100 is firstsupplied to the pre-emphasis circuit 10, at which high frequencycomponents thereof are emphasized, and then to the FM modulator 11, atwhich it is FM modulated to obtain an FM video signal. Meanwhile, anaudio signal inputted to the recording system by way of an audio signalinput terminal 101 is supplied to the PCM encoder 12, at which theprocess of shuffling, addition of an error correction code and so forthis performed therefor and then time base compressing process isperformed for the thus processed audio signal in order to allow theaudio signal for one field period to be later inserted into a fixedportion of a vertical blanking period of the FM video signal as seen inFIG. 53. The PCM encoder 12 outputs the thus PCM modulated audio signaltherefrom. The PCM modulated audio signal from the PCM encoder 12 andthe FM modulated video signal from the FM modulator 11 are thenalternatively selected by the switches 13 and 14, that is, selectivelytransmitted to the adder 15 in accordance with a suitable changing overoperation of the switches 13 and 14 so that they are added to each othersuch that the PCM audio signal may be recorded in a recording area whichis provided at a fixed portion of a vertical blanking period of an FMmodulated video signal as seen in FIG. 54 thereby to produce a recordingsignal. The recording signal is supplied to the recording amplifier 16,at which the FM video signal and the PCM audio signal thereof areamplified. The composite recording signal of the FM video signal and thePCM audio signal is then recorded onto a magnetic tape 200 by means ofthe recording video head 17.

On the other hand, upon reproduction, such FM video signal and PCM audiosignal recorded in a mixed condition on the magnetic tape 200 arereproduced from the magnetic tape 200 by means of the reproducing videohead 18 and amplified as a reproduction signal by the reproductionamplifier 19. The thus amplified reproduction signal is transmitted tothe reproduction equalizer 20 and also to the PCM decoder 23. At the PCMdecoder 23, a PCM audio signal for one field inserted in a verticalblanking period of such reproduction signal is detected and thenprocessed by time base elongation, error correction, de-shuffling, errormodification and so forth to restore an original audio signal. The thusrestored original audio signal by the PCM decoder 23 is then outputtedas a reproduction output audio signal of the reproducing system by wayof a reproduction audio signal output terminal 103.

In the meantime, the reproduction equalizer 20 compensates for afrequency characteristic of the reproduction FM video signal in thereproduction signal received from the reproduction amplifier 19, and anoutput of the reproduction equalizer 20 is inputted to and FMdemodulated by the FM demodulator 21. The FM demodulated video signal isthen inputted to the de-emphasis circuit 22, at which high frequencycomponents thereof, which were emphasized upon recording, arede-emphasized to restore an original video signal. The thus restoredreproduction video signal is then inputted to the clamp circuit 24, atwhich it is clamped so that it may have a voltage within a voltage rangeapplicable for the A/D converter 25 at a next stage. It is to be notedthat, at the clamp circuit 24, a synchronizing signal of thereproduction video signal is separated to produce a clamp pulse and aleading end portion of the synchronizing signal of the reproductionvideo signal is clamped to a predetermined dc voltage level in responseto such clamp pulse. The thus clamped reproduction video signal from theclamp circuit 24 is then converted from an analog signal to a digitalsignal by the A/D converter 25 and then transmitted to the reproductionsignal processing circuit 27. The clamped reproduction video signal isalso transmitted to the synchronizing separator circuit 26, at which asynchronizing signal is separated therefrom. The reproduction signalprocessing circuit 27 performs reproduction signal processing such astime base correction and dropout compensation of the reproduction videosignal from the A/D converter 25 in accordance with a synchronizingseparation output of the synchronizing separator circuit 26, and anoutput reproduction video signal of the reproduction signal processingcircuit 27 is converted from a digital signal back into an analog signalby the D/A converter 28 and outputted as a reproduction output videosignal of the reproducing system by way of a reproduction video signaloutput terminal 102.

In the conventional magnetic recording and reproducing apparatus in theform of a video tape recorder described above, an FM modulated videosignal and a PCM audio signal are added, upon recording, to each otherin accordance with a suitable changing over operation in a fixed portionof a blanking period of the FM video signal. On the other hand, uponreproduction, a reproduction FM video signal and a PCM audio signal,which was mixed with such FM video signal upon recording, are FMdemodulated as they are. Consequently, a reproduction video signalincluding such reproduction FM video signal and PCM audio signalpresents such an output signal waveform as shown in FIG. 54 as if itincludes noises in a PCM audio signal region.

Further, before processing such as FM demodulation of a reproductionsignal in which a PCM audio signal is inserted is performed, an FM videosignal and such PCM audio signal are separated from each other. In thisinstance, a period of a PCM audio signal region of the reproduction FMvideo signal from which the PCM audio signal has been separated makes ano signal portion, and if the reproduction FM video signal having suchno-signal portion is FM demodulated, then the waveform of the FMdemodulated video signal presents such an output signal waveform asshown in FIG. 54 as if it includes noises in its PCM audio signal regionwhich is a no-signal portion similarly as described above.

If such a noise signal waveform as seen in FIG. 54 is included in a PCMaudio signal region of a reproduction FM video signal, normalsynchronizing separation cannot be performed with such reproduction FMvideo signal. In particular, where the clamp circuit 24, whichconstitutes together with the A/D converter 25, synchronizing separatorcircuit 26, reproduction signal processing circuit 27 and D/A converter28 a time base corrector by which a time base variation of areproduction video signal caused by elongation of a video tape or thelike is time base corrected by detection of an interval of time betweenadjacent synchronizing signals to re-set a synchronizing signal to acorrect position, is constructed such that it separates a synchronizingsignal of a reproduction video signal to produce a clamp pulse andclamps an end of a synchronizing signal in accordance with such clamppulse, if such a noise waveform is included in a PCM audio signalregion, correct synchronizing separation cannot be performed with suchreproduction video signal, but the clamp circuit 24 will perform aclamping operation at a lower end of a noise portion in the PCM audiosignal region. Consequently, the clamp circuit at the input of theanalog to digital converter does not operate normally and a time basecorrecting operation cannot be performed appropriately, which makes areproduction picture image unstable or abnormal.

Another exemplary conventional magnetic recording and reproducingapparatus is shown in FIG. 55. Referring to FIG. 55, the magneticrecording and reproducing apparatus shown includes a recording systemincluding an analog to digital (A/D) converter 1 for converting an inputvideo signal from an analog signal into a digital signal, a firstsynchronizing separator circuit 2 for separating a synchronizing signalfrom an input video signal, a recording signal processing circuit 3 forperforming such recording signal processing as to insert blanking data,which make, upon reproduction, a reference signal for such processing astime base correction, into a video signal in accordance with asynchronizing signal from the first synchronizing separator 2, avertical blanking data generator 4 for generating, in accordance with asynchronizing separation signal from the first synchronizing separatorcircuit 2, blanking data for a vertical blanking period of a videosignal, a gate pulse for enabling vertical blanking data to be insertedinto video signal data from the recording signal processing circuit 3and a timing pulse for inserting a PCM audio signal into an FM videosignal, a selector 5 for inserting vertical blanking data from thevertical blanking data generator 4 into video signal data from therecording signal processing circuit 3, and a digital to analog (D/A)converter 6 for converting an output signal of the selector 5 from adigital signal into an analog signal. The recording system of themagnetic recording and reproducing apparatus further includes an FMmodulator 11, a PCM encoder 12, a pair of switches 13 and 14, an adder15, a recording amplifier 16 and a recording video head 17, which aresimilar to the FM modulator 11, PCM encoder 12, switches 13 and 14,adder 15, recording amplifier 16 and recording video head 17,respectively, of the recording system of the magnetic recording andreproducing apparatus shown in FIG. 52. It is to be noted that thepre-emphasis circuit 10 of the magnetic recording and reproducingapparatus of FIG. 52 is omitted from the magnetic recording andreproducing apparatus of FIG. 55 and an output digital signal of the D/Aconverter 6 is inputted to the FM modulator 11.

The magnetic recording and reproducing apparatus further includes areproducing system which is similar in construction to but onlydifferent from the reproducing system of the magnetic recording andreproducing apparatus shown in FIG. 52 in that it does not include thede-emphasis circuit 22. It is to be noted that, since the recordingsystem includes the first synchronizing separator circuit 2, thesynchronizing separator circuit 26 may be hereinafter referred to assecond synchronizing separator circuit.

In operation, an input video signal is first converted from an analogsignal into a digital signal by the A/D converter 1 and then outputtedto the recording signal processing circuit 3. Meanwhile, the input videosignal is inputted also to the first synchronizing separator circuit 2,at which a synchronizing signal is separated from the input videosignal. At the recording signal processing circuit 3, such recordingsignal processing as to insert blanking data, which make, uponreproduction, a reference signal for such processing as time basecorrection, into a video signal is performed in accordance with anoutput signal from the first synchronizing separator 2, and the thusprocessed signal is transmitted from the recording signal processingcircuit 3 to the selector 5. Meanwhile, at the vertical blanking datagenerator 4, vertical blanking data for a video signal are generatedwith reference to the output of the first synchronizing separatorcircuit 2 and outputted to the selector 5. Here, the vertical blankingdata generator 4 further operates to generate a gate pulse for enablingvertical blanking data to be inserted into video signal data outputtedfrom the recording signal processing circuit 3 and a timing pulse forinserting a PCM audio signal into an FM video signal.

At the selector 5, the vertical blanking data received from the verticalblanking data generator 4 are inserted into the video signal datareceived from the recording signal processing circuit 3 with referenceto a gate pulse from the vertical blanking data generator 4. Then, anoutput of the selector 5 is converted from a digital signal into ananalog signal by the D/A converter 6. A typical waveform of suchrecording video signal outputted from the D/A converter 6 is shown inFIG. 56. The recording video signal outputted from the D/A converter 6is subsequently supplied to the FM modulator 11 while an input audiosignal is supplied to the PCM encoder 12, whereafter the video signaland audio signal are processed by the FM modulator 11 and PCM encoder12, switches 13 and 14, adder 15 and recording amplifier 16 and recordedonto a magnetic tape 200 by means of the recording video head 17 in asimilar manner as in the magnetic recording and reproducing apparatus ofFIG. 52 described hereinabove. It is to be noted here that changing overoperations of the switches 13 and 14 are performed in response to atiming pulse transmitted thereto from the vertical blanking datagenerator 4. Also the PCM encoder 12 operates in response to such timingpulse from the vertical blanking data generator 4.

The thus recorded video signal and audio signal are reproduced from themagnetic tape 200 by means of the reproducing video head 18 andprocessed in a similar manner as in the reproducing system of themagnetic recording and reproducing apparatus of FIG. 52 except that anFM demodulated reproduction video signal from the FM demodulator 21 issupplied directly to the clamp circuit 24 without being processed by anyde-emphasis circuit because pre-emphasis has not been performed for arecording video signal in the recording system.

Also in the conventional magnetic recording and reproducing apparatus ofFIG. 55, an FM modulated video signal and a PCM audio signal are added,upon recording, to each other in accordance with a suitable changingover operation such that the PCM audio signal is inserted into a fixedportion of a blanking period of the FM video signal. On the other hand,upon reproduction, a reproduction FM video signal and a reproduction PCMaudio signal, which was mixed with such FM video signal upon recording,are FM demodulated as they are. On the other hand, since a PCM audiosignal has a waveform of pulses, it includes wide band signalcomponents, and consequently, it is not certain what waveform a videosignal after demodulation has in a PCM audio signal region as seen froma waveform shown in FIG. 54. Rather, it has such a signal waveform as ifit includes noises in a PCM audio signal region.

Further, also in such a case that an FM video signal and such PCM audiosignal are separated from each other as seen from a waveform (b) of FIG.57 before processing such as FM demodulation of a reproduction signal inwhich a PCM audio signal is inserted as seen from another waveform (a)of FIG. 57 is performed, a period of a PCM audio signal region of thereproduction FM video signal (waveform (b) of FIG. 57) from which thePCM audio signal has been removed makes a no-signal portion, and if thereproduction FM video signal having such no-signal portion is FMdemodulated, then the waveform of the FM demodulated video signalpresents such an output signal waveform (c) as shown in FIG. 57 as if itincludes noises in its PCM audio signal region which is the no-signalportion, similarly as described.

If such a noise signal waveform (c) as seen in FIG. 57 is included in aPCM audio signal region of a reproduction FM video signal, normalsynchronizing separation cannot be performed with such reproduction FMvideo signal. In particular, where the clamp circuit 24 at a precedingstage to the A/D converter 25 is constructed such that it separates asynchronizing signal of a reproduction video signal to produce a clamppulse and clamps an end of a synchronizing signal in accordance withsuch clamp pulse, if such a noise waveform (c) as seen in FIG. 57 isincluded in a PCM audio signal region, correct synchronizing separationcannot be performed with such reproduction video signal, but the clampcircuit 24 will perform a clamping operation at a lower end of a noiseportion in the PCM audio signal region. Consequently, the clamp circuit24 at the input of the analog to digital converter 25 will not operatenormally and a time base correcting operation cannot be performedappropriately, which makes a reproduction picture image unstable orabnormal.

Further, it is not certain what waveform a video signal has, afterdemodulation, in a PCM audio signal region of a reproduction videosignal, and if a noise is outputted at a higher level than a white levelof a video signal or at a level lower than an end of a synchronizingsignal as seen in FIG. 54 or else a dc component is included, such noisewill cause a sag, by which the reproduction video signal is partiallyvaried in hue. Consequently, a good reproduction video signal cannot beobtained.

A further exemplary conventional magnetic recording and reproducingapparatus is shown in FIG. 59. Referring to FIG. 59, the magneticrecording and reproducing apparatus shown includes a recording systemwhich is similar in construction to the recording system of the magneticrecording and reproducing apparatus shown in FIG. 55 except that itincludes a recording signal processing circuit 7 in place of therecording signal processing circuit 3, vertical blanking data generator4 and selector 5 of the magnetic recording and reproducing apparatus ofFIG. 55 and additionally includes a pre-emphasis circuit 10 connected tothe recording signal processing circuit 7. The recording signalprocessing circuit 7 performs recording signal processing such as toinsert blanking data into an input video signal with reference to asynchronizing signal outputted from the first synchronizing separatorcircuit 2. The recording signal processing circuit 7 further operates togenerate a timing pulse for inserting a PCM audio signal into an FMvideo signal. Such timing signal is transmitted to the PCM encoder 12and switches 13 and 14. An input video signal processed by the recordingsignal processing circuit 7 is inputted to the D/A converter 6, at whichit is converted from a digital signal into an analog signal. An analogoutput video signal of the D/A converter 6 is inputted to thepre-emphasis circuit 10, at which high frequency components thereof areemphasized, and then inputted to the FM modulator 11. It is to be notedthat the magnetic recording and reproducing apparatus includes a pair ofrotary heads 29a and 29b which each acts as a recording head uponrecording and as a reproducing head upon reproduction.

The magnetic recording and reproducing apparatus further includes areproducing system which is also similar in construction to thereproducing system of the magnetic recording and reproducing apparatusof FIG. 55 in that it includes a pair of reproduction amplifier 19a andreproduction amplifier 19b and a PCM decoder 31 in place of the singlereproduction amplifier 19 and the PCM decoder 23, respectively, andadditionally includes a head changing over circuit 30 interposed betweenthe reproduction amplifiers 19a and 19b and head changing over circuit30, a limiter 32 interposed between the reproduction equalizer 20 and FMdemodulator 21 and a de-emphasis circuit 22 interposed between the FMdemodulator 21 and clamp circuit 24. The reproduction amplifiers 19a and19b amplify reproduction signals from the rotary heads 29a and 29b,respectively, and the thus amplified reproduction signals areselectively received by the head changing over circuit 30 in response toa head changing over signal. The PCM decoder 31 may be similar inconstruction to the PCM decoder 23 described hereinabove. The limiter 32receives an output reproduction FM video signal of the reproductionequalizer 20 and removes amplitude variation components from thereceived reproduction FM video signal. The de-emphasis circuit 22 has areverse characteristic to that of the pre-emphasis circuit 10 of therecording system.

Referring to FIG. 60, the rotary heads 29a and 29b are shown as viewedfrom above. The rotary heads 29a and 29b are mounted on a rotary drum 44in an angularly spaced relationship by 180 degrees from each other. Amagnetic tape 200 is wrapped over about 180 degrees around an outerperiphery of the rotary drum 44 under the guidance of a pair of guidepins 45a and 45b and fed in a direction indicated by an arrow mark bythe rotary drum 44 when the rotary drum 44 rotates in a counterclockwisedirection in FIG. 60.

In operation, an input video signal is first converted from an analogsignal into a digital signal by the A/D converter 1 and then outputtedto the recording signal processing circuit 3. At the recording signalprocessing circuit 3, such recording signal processing as to insertblanking data is performed in accordance with a synchronizing separationoutput of the first synchronizing separator 2. The recording signalprocessing circuit 3 also generates and outputs a timing pulse forinserting a PCM audio signal into an FM video signal. An outputrecording signal of the recording signal processing circuit 3 isconverted from a digital signal into an analog signal by the D/Aconverter 6 and then inputted to the pre-emphasis circuit 10, at whichhigh frequency components thereof are emphasized. The recording videosignal is subsequently inputted to the FM modulator 11 while an inputaudio signal is supplied to the PCM encoder 12, whereafter the videosignal and audio signal are processed by the FM modulator 11 and PCMencoder 12, switches 13 and 14, adder 15 and recording amplifier 16 in asimilar manner as in the magnetic recording and reproducing apparatus ofFIGS. 52 and 55 described hereinabove and then recorded onto a magnetictape 200 by means of the rotary heads 29a and 29b. It is to be notedhere that changing over operations of the switches 13 and 14 areperformed in response to a timing pulse transmitted thereto from therecording signal processing circuit 7. Also the PCM encoder 12 operatesin response to such timing pulse from the vertical blanking datagenerator 4.

In this instance, since the magnetic tape 200 is wrapped over a littlegreater than 180 degrees as seen in FIG. 60 on the outer periphery ofthe rotary drum 44, even if recording electric current flows alwaysthrough the rotary heads 29a and 29b, recording on the magnetic tape 200takes place only while a rotary head is in contact with the magnetictape 200 within the angular range. Accordingly, the magnetic tape hassuch record pattern as illustrated in FIG. 61 wherein information isrecorded in two regions a and b while the rotary drum 44 makes one fullrotation such that a recording signal for one field is recorded onto onetrack. It is to be noted that, in FIG. 61, reference character a denotesa track recorded by the rotary head 29a while reference character bdenotes a track recorded by the other rotary head 29b. Further, since aPCM audio signal is recorded in a time division multiplexed condition ina vertical blanking period of an FM video signal, such PCM audio signalis recorded at each of hatched portions of the tracks a and b.

The thus recorded FM video signal and PCM audio signal are reproducedfrom the magnetic tape 200 by means of the rotary heads 29a and 29b andthen amplified by the reproducing amplifiers 19a and 19b. Then, thereproduction signals outputted from the reproduction amplifiers 19a and19b are alternatively selected by the head changing over circuit 30 inresponse to a head changing over signal such that a reproduction signalof a rotary head which is currently in contact with the magnetic head200 may be selected to form such a single reproduction signal as shownby a waveform (c) of FIG. 62 as seen from waveforms (a) and (b) of FIG.62. The reproduction signal from the head changing over circuit 30 isthen transmitted to the reproduction equalizer 20 and also to the PCMdecoder 31. At the PCM decoder 31, a PCM audio signal for one fieldinserted in a vertical blanking period of the received reproductionsignal is detected and then such signal processing as error correction,de-shuffling, error modification and so forth is performed for the thusdetected PCM audio signal to restore an original audio signal. The thusrestored audio signal is outputted as an output signal of the recordingsystem from the PCM decoder 31.

Generally, when an FM signal is recorded or reproduced by means of anelectromagnetic converting system employing a tape and a head, lowerside band waves are emphasized while upper side band waves aresuppressed, and consequently, a modulation index is varied and animbalance of side band waves is produced simultaneously. As a result, areproduction FM signal which corresponds to a rising portion (waveform(a) in FIG. 63) of a video signal having high frequency componentsemphasized by the pre-emphasis circuit 10 is distorted significantly asseen from a waveform (b) of FIG. 63. Thus, at the reproduction equalizer20, lower side band waves are suppressed while upper side band waves areemphasized in such a frequency characteristic as, for example, shown inFIG. 64 thereby to compensate for a frequency characteristic of thereproduction FM video signal. As a result, an output of the reproductionequalizer 20 is reduced in distortion as seen from a waveform (c) ofFIG. 63. The output of the reproduction equalizer 20 is transmitted tothe limiter 32, at which amplitude variation components of thereproduction FM video signal are removed. The limiter 32 thus developssuch an output as shown by a waveform (d) in FIG. 63.

The reproduction signal outputted from the limiter 32 is inputted to andFM demodulated by the FM demodulator 21, and then high frequencycomponents which were emphasized upon recording are de-emphasized by thede-emphasis circuit 22 to obtain a reproduction video signal which arereduced in high frequency noises. The thus obtained reproduction videosignal is then inputted to the clamp circuit 24 and thereafter processedby the clamp circuit 24, A/D converter 25, second synchronizingseparator circuit 26, reproduction signal processing circuit 27 and D/Aconverter 28 to produce an output analog reproduction video signal in asimilar manner as in the recording system of the magnetic recording andreproducing apparatus of FIG. 52 described hereinabove.

Also in the conventional magnetic recording and reproducing apparatus, aPCM audio signal is time division multiplexed, upon recording, into avertical blanking period of an FM modulated video signal, and uponreproduction, such reproduction FM video signal and PCM audio signalmixed with such FM video signal are FM demodulated as they are. On theother hand, since a PCM audio signal is a waveform of pulses, itincludes wide band signal components, and consequently, a PCM audiosignal band will overlap with a video signal band as seen from FIG. 65.In such case, if a reproduced FM video signal and a PCM audio signal areFM demodulated as described above, it is not certain in what waveform anoutput of the FM demodulator 21 is demodulated in a PCM audio signalregion. Rather, the output of the FM demodulator 21 presents such anoutput signal waveform as shown in FIG. 54 as if it includes noises in aPCM audio signal region.

Further, also in such a case that an FM video signal and such PCM audiosignal are separated from each other as seen from the waveform (b) ofFIG. 57 before processing such as FM demodulation of a reproductionsignal shown by the waveform (a) of FIG. 57 is performed, a period ofthe PCM audio signal region of the reproduction FM video signal(waveform (b) of FIG. 57) makes a no-signal portion, and if thereproduction FM video signal having such no-signal portion is FMdemodulated, the waveform of the FM demodulated video signal presentssuch output signal waveform (c) as shown in FIG. 57 as if it includesnoises in its PCM audio signal region which is the non signal portionsimilarly as described above.

Where the clamp circuit 24 at a preceding stage to the A/D converter 25is constructed such that it separates a synchronizing signal of areproduction video signal to produce a clamp pulse and clamps an end ofa synchronizing signal in accordance with such clamp pulse, if such anoise waveform (c) as seen in FIG. 57 is included in a PCM audio signalregion of a reproduction video signal, correct synchronizing separationcannot be performed with such reproduction video signal, but the clampcircuit 24 will perform a clamping operation at a lower end of a noiseportion in the PCM audio signal region. Consequently, the signal levelof an input reproduction video signal to the A/D converter 25 cannot beclamped at a normal value, which makes a reproduction picture imageunstable or abnormal.

Further, if it is not uncertain in what waveform an output of the FMdemodulator 21 is demodulated in a PCM audio signal region of areproduction video signal and the output of the FM demodulator 21 hasnoises above a white level or below an end of a synchronizing signal asseen in FIG. 54 or has a dc component, such noise may cause a sag, bywhich the reproduction video signal will partially be varied in hue.Consequently, a good reproduction video signal cannot be obtained.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a magnetic recordingand reproducing apparatus wherein synchronizing separation of areproduction video signal can be performed accurately and a stabilizedreproduction video signal can be obtained.

It is another object of the present invention to provide a magneticrecording and reproducing apparatus wherein synchronizing separation ofa reproduction video signal can be performed to assure a correctoperation of a clamp circuit and sags can be reduced to assure astabilized good reproduction video signal.

In order to attain the objects, according to one aspect of the presentinvention, there is provided a magnetic recording and reproducingapparatus of the type wherein a video signal is FM modulated andrecorded onto and reproduced from a magnetic medium by means of a rotaryhead, comprising changing over switch means for selectively inserting,upon recording, a PCM modulated audio signal into a blanking period ofan FM modulated video signal, a PCM region signal generator foridentifying a region of a PCM modulated audio signal in a reproductionsignal reproduced by the rotary head and generating a control signalrepresentative of a PCM audio signal region, FM demodulating means forFM demodulating a reproduction signal from the rotary head into areproduction FM demodulation signal, and a clip circuit for clipping alower end portion of a PCM audio signal region of a reproduction FMdemodulation signal from the FM demodulating means in accordance with acontrol signal generated from the PCM region signal generator.

With the magnetic recording and reproducing apparatus, lower endportions of noise in a PCM audio signal region of a reproduction FMdemodulation signal are clipped at a level equal to or around a pedestallevel in accordance with a control signal generated from the PCM regionsignal generator and representative of a PCM audio signal region.Consequently, synchronizing separation of a reproduction video signalcan be performed accurately, and a stabilized reproduction video signalcan be obtained.

According to another aspect of the present invention, there is provideda magnetic recording and reproducing apparatus of the type wherein avideo signal is FM modulated and a digital audio signal is time divisionmultiplexed into a blanking period of the FM modulated video signal andrecorded onto and reproduced from a magnetic record medium by means of arotary head, comprising control signal generating means for identifying,upon reproduction, a digital audio signal region of a reproductionsignal reproduced by the rotary head and generating a control signalrepresentative of such digital audio signal region, level signalgenerating means for generating a signal having a predetermined levelwith respect to a video signal, FM demodulating means for FMdemodulating a reproduction signal from the rotary head, and a switchcircuit for selecting one of an FM demodulation signal from the FMdemodulating means and an output of the level signal generating means inaccordance with an output of the control signal generating means.

With the magnetic recording and reproducing apparatus, the controllingsignal generating means identifies a digital audio signal region of areproduction signal reproduced by the rotary head and generates acontrol signal representative of such digital audio signal region.Meanwhile, a signal having a predetermined level with respect to a videosignal is generated by level signal generating means, and thereproduction signal is FM modulated by FM demodulating means. The switchcircuit selects one of an FM demodulation signal from the FMdemodulating means and an output of the level signal generating means inaccordance with an output of the control signal generating means.Consequently, the signal in the digital audio signal region of the FMmodulated reproduction signal is made a signal having a fixed level.Accordingly, synchronizing separation of a reproduction video signal canbe performed accurately, and a stabilized video signal can be obtained.

According to a further aspect of the present invention, there isprovided a magnetic recording and reproducing apparatus of the typewherein a video signal is FM modulated and a digital audio signal istime division multiplexed into a blanking period of the FM modulatedvideo signal and recorded onto and reproduced from a magnetic recordmedium by means of a rotary head, comprising control signal generatingmeans for identifying, upon reproduction, a digital audio signal regionof a reproduction signal reproduced by the rotary head and generating acontrol signal representative of such digital audio signal region,signal generating means for generating a signal of a predeterminedfrequency, and a switch circuit for selecting one of a reproductionsignal from the rotary head and an output of the signal generating meansin accordance with an output of the control signal generating means.

With the magnetic recording and reproducing apparatus, the controlsignal generating means identifies a digital audio signal region of areproduction signal reproduced by the rotary head and generates acontrol signal representative of such digital audio signal region.Meanwhile, a signal of a predetermined frequency which is to make afixed level signal with respect to a video signal after demodulation isgenerated by signal generating means. The switch circuit selects one ofa reproduction signal from the rotary head and an output of the signalgenerating means in accordance with an output of the control signalgenerating means. Consequently, the signal in the digital audio signalregion of the FM modulated reproduction signal is made a signal having afixed level. Accordingly, synchronizing separation of a reproductionvideo signal can be performed accurately, and a stabilized video signalcan be obtained.

According to a still further aspect of the present invention, there isprovided a magnetic recording and reproducing apparatus of the typewherein a video signal is FM modulated and a digital audio signal istime division multiplexed into a blanking period of the FM modulatedvideo signal and recorded onto and reproduced from a magnetic recordmedium by means of a rotary head, comprising region signal generatingmeans for identifying a region of a digital audio signal in areproduction signal reproduced by the rotary head and generating acontrol signal representative of a region of a digital audio signal. FMdemodulating means for FM demodulating a reproduction signal from therotary head, and a clip circuit for clipping an upper end portion and alower end portion in a digital audio signal region of an FM demodulationsignal from the FM demodulator in accordance with an output signal ofthe region signal generating means.

With the magnetic recording and reproducing apparatus, upper endportions and lower end portions of noises in a digital audio signalregion of an FM demodulated reproduction video signal are clipped inaccordance with a digital region signal representative of such digitalaudio signal region. Consequently, synchronizing separation of areproduction video signal can be performed accurately, which assures anormal operation of a clamp circuit. Accordingly, sags can be reduced.

According to a yet further aspect of the present invention, there isprovided magnetic recording and reproducing apparatus of the typewherein a video signal is FM modulated and a digital audio signal istime division multiplexed into a blanking period of the FM modulatedvideo signal and recorded onto and reproduced from a magnetic recordmedium by means of a rotary head, comprising region signal generatingmeans for identifying a region of a digital audio signal in areproduction signal reproduced by the rotary head and generating acontrol signal representative of a region of a digital audio signal,signal generating means for generating a signal of a predeterminedfrequency, FM demodulating means for FM demodulating a reproductionsignal from the rotary head, and changing over means for selecting oneof an FM demodulation signal from the FM demodulating means and anoutput of the signal generating means in accordance with an outputsignal of the region signal generating means.

With the magnetic recording and reproducing apparatus, a signal in adigital audio signal region of an FM demodulated reproduction videosignal is changed into a signal of a fixed frequency in accordance witha digital region signal representative of such digital audio signalregion. Consequently, synchronizing separation of a reproduction videosignal can be performed accurately, which assures a normal operation ofa clamp circuit. Accordingly, sags can be reduced.

According to a yet further aspect of the present invention, there isprovided a magnetic recording and reproducing apparatus of the typewherein a video signal is FM modulated and a digital audio signal istime division multiplexed into a blanking period of the FM modulatedvideo signal and recorded onto and reproduced from a magnetic recordmedium by means of a rotary head, comprising region signal generatingmeans for identifying a region of a digital audio signal in areproduction signal reproduced by the rotary head and generating acontrol signal representative of a region of a digital audio signal, FMdemodulating means for FM demodulating a reproduction signal from therotary head, delaying means for delaying an FM demodulation signal fromthe FM demodulating means by a fixed period of time, and change overmeans for selecting one of an FM demodulation signal from the FMdemodulating means and an output of the delaying means in accordancewith an output signal of the region signal generating means.

With the magnetic recording and reproducing apparatus, a signal in adigital audio signal region of an FM demodulated reproduction videosignal is replaced, in accordance with a digital region signalrepresentative of such digital audio signal region, by data of a lastline of a preceding field to the digital audio signal region.Consequently, synchronizing separation of a reproduction video signalcan be performed accurately, which assures a normal operation of a clampcircuit. Accordingly, sags can be reduced.

According to a yet further aspect of the present invention, there isprovided video signal recording and reproducing apparatus of the typewherein a video signal is FM modulated and a digital audio signal istime division multiplexed into a blanking period of the FM modulatedvideo signal and recorded onto and reproduced from a magnetic recordmedium by means of a rotary head, comprising blanking data generatingmeans for generating, upon recording and reproduction, blanking data ofa video signal, region signal generating means for identifying, uponreproduction, a region of a digital audio signal in a reproductionsignal reproduced by the rotary head and generating a control signalrepresentative of such region of the digital audio signal, FMdemodulating means for FM demodulating a reproduction signal from therotary head, and changing over means for selecting one of an FMdemodulation signal from the FM demodulating means and an output of theblanking data generating means in accordance with an output signal ofthe region signal generating means.

With the video signal recording and reproducing apparatus, an FMdemodulated reproduction video signal is partially replaced by avertical blanking signal generated by the blanking data generating meansin a recording system so that the vertical blanking signal may be asignal in a digital audio signal region of the FM demodulatedreproduction video signal. Consequently, synchronizing separation of areproduction video signal can be performed accurately, which assures anormal operation of a clamp circuit. Accordingly, a good reproductionvideo signal can be obtained and sags can be reduced.

According to a yet further aspect of the present invention, there isprovided a video signal recording and reproducing apparatus of the typewherein a video signal is FM modulated and a digital audio signal istime division multiplexed into a blanking period of the FM modulatedvideo signal and recorded onto and reproduced from a magnetic recordmedium by means of a rotary head, comprising blanking data generatingmeans for generating, upon recording and reproduction, blanking data ofa video signal, FM modulating means for FM modulating, upon recordingand reproduction, blanking data of a video signal generated from theblanking data generating means, region signal generating means foridentifying, upon reproduction, a region of a digital audio signal in areproduction signal reproduced by the rotary head and generating acontrol signal representative of such region of the digital audiosignal, and changing over means for selecting one of a reproductionsignal from the rotary head and an output of the FM modulating means inaccordance with an output signal of the region signal generating means.

With the video signal recording and reproducing apparatus, areproduction video signal before FM demodulation is partially replacedby a vertical blanking signal generated by the blanking data generatingmeans in a recording system so that a signal obtained by FM demodulationof the vertical blanking signal may be a signal in a digital audiosignal region of such reproduction video signal after FM demodulation.Consequently, synchronizing separation of a reproduction video signalcan be performed accurately, which assures a normal operation of a clampcircuit. Accordingly, a good reproduction video signal can be obtainedand sags can be reduced.

According to a yet further aspect of the present invention, there isprovided a magnetic recording and reproducing apparatus of the typewherein a video signal is FM modulated and a PCM modulated audio signalis inserted into a blanking period of the FM modulated video signal andrecorded onto and reproduced from a magnetic record medium by means of arotary head, comprising a PCM region signal generator for identifying aregion of a PCM modulated audio signal in a reproduction signalreproduced by the rotary head and generating a control signalrepresentative of such PCM audio signal region, an analog to digitalconverter for converting a reproduction signal of the rotary head into adigital signal, and storage means for storing therein a digitalreproduction signal from the analog to digital converter and reading outthe stored digital signal therefrom in accordance with an output of thePCM region signal generating means in such a manner as to remove a PCMaudio signal from the digital reproduction signal.

With the magnetic recording and reproducing apparatus, a reproductionsignal is once changed from an analog signal into a digital signal andthen stored in the form of a digital signal in the storage means, andthen the reproduction signal is read out from the storage means inaccordance with a control signal representative of a PCM audio signalregion in such a manner as to remove a PCM audio signal from the digitalreproduction signal. Consequently, a reproduction video signal after FMdemodulation is free from noise, and synchronizing separation of areproduction video signal can be performed accurately and a stabilizedreproduction video signal can be obtained.

According to a yet further aspect of the present invention, there isprovided a magnetic recording and reproducing apparatus of the typewherein a video signal is FM modulated and a PCM modulated audio signalis inserted into a blanking period of the FM modulated video signal andrecorded onto and reproduced from a magnetic record medium by means of arotary head, comprising a PCM region signal generator for identifying aregion of a PCM modulated audio signal in a reproduction signalreproduced by the rotary head and generating a control signalrepresentative of such PCM audio signal region, and storage means forstoring therein a reproduction signal from the rotary head in the formof an analog signal and reading out,the stored analog signal therefromin accordance with an output of the PCM region signal generating meansin such a manner as to remove a PCM audio signal from the reproductionsignal.

With the magnetic recording and reproducing apparatus, a reproductionsignal is stored in the form of an analog signal into the storage meansand then read out from the storage means in accordance with a controlsignal representative of a PCM audio signal region in such a manner asto remove a PCM audio signal from the analog reproduction signal.Consequently, a reproduction video signal after FM demodulation is freefrom noise, and synchronizing separation of a reproduction video signalcan be performed accurately and a stabilized reproduction video signalcan be obtained.

According to a yet further aspect of the present invention, there isprovided a video signal recording and reproducing apparatus of the typewherein a video signal is FM modulated and a digital audio signal istime division multiplexed into a blanking period of the FM modulatedvideo signal and recorded and reproduced, comprising region signalgenerating means for identifying, upon reproduction, a region of adigital audio signal in a reproduction signal and generating a controlsignal representative of such region of the digital audio signal,delaying means for delaying the reproduction signal by a fixed period oftime, and changing over means for selecting one of the reproductionsignal and an output of the delaying means in accordance with an outputsignal of the region signal generating means.

With the video signal recording and reproducing apparatus, the changingover means selects, in accordance with a digital region signalrepresentative of a digital audio signal region, one of a reproductionsignal and an output of the delaying means which delays the reproductionsignal by a fixed period of time, and an output of the changing overmeans is FM demodulated.. Consequently, a signal in the digital audiosignal region of the reproduction video signal is replaced by areproduction video signal of a preceding field. Consequently,synchronizing separation of a reproduction video signal can be performedaccurately, which assures a normal operation of a clamp circuit.Accordingly, a good reproduction picture image can be obtained. Further,a signal also in a digital audio signal region can be clamped, and sagscan be reproduced.

According to a yet further aspect of the present invention, there isprovided a video signal recording and reproducing apparatus of the typewherein a video signal is FM modulated and a digital audio signal istime division multiplexed into a blanking period of the FM modulatedvideo signal and recorded and reproduced, comprising region signalgenerating means for identifying, upon reproduction, a region of adigital audio signal in a reproduction signal and generating a controlsignal representative of such region of the digital audio signal,delaying means for delaying the reproduction signal by a fixed period oftime equal to a horizontal scanning period of the recording signal, andchanging over means for selecting one of the reproduction signal and anoutput of the delaying means in accordance with an output signal of theregion signal generating means.

With the video signal recording .and reproducing apparatus, the changingover means selects, in accordance with a digital region signalrepresentative of a digital audio signal region, one of a reproductionsignal and an output of the delaying means which delays the reproductionsignal by a fixed period of time equal to a horizontal scanning periodof the recording signal, and an output of the changing over means is FMdemodulated. Consequently, a signal in the digital audio signal regionof the reproduction video signal is replaced by a video signal of arepetition of data of a last line of a preceding field. Consequently,synchronizing separation of a reproduction video signal can be performedaccurately, which assures a normal operation of a clamp circuit.Accordingly, a good reproduction picture image can be obtained. Further,a signal also in a digital audio signal region can be clamped, and sagscan be reproduced.

According to a yet further aspect of the present invention, there isprovided a video signal recording and reproducing apparatus of the typewherein a video signal is FM modulated and a digital audio signal istime division multiplexed into a blanking period of the FM modulatedvideo signal and recorded and reproduced, comprising region signalgenerating means for identifying, upon reproduction, a region of adigital audio signal in a reproduction signal and generating a controlsignal representative of such region of the digital audio signal, FMsignal generating means for FM modulating a signal of a predeterminedfrequency to develop an FM modulated signal, and changing over means forselecting one of the reproduction signal and the FM modulated signalfrom the FM signal generating means in accordance with an output signalof the region signal generating means.

With the video signal recording and reproducing apparatus, the changingover means selects, in accordance with a digital region signalrepresentative of a digital audio signal region, one of a reproductionsignal and an FM demodulated signal obtained by FM demodulation of asignal of a predetermined frequency so that a signal in the digitalaudio signal region of the reproduction video signal after FMdemodulation may be a signal of the fixed frequency. Consequently,synchronizing separation of a reproduction video signal can be performedaccurately, which assures a normal operation of a clamp circuit.Accordingly, a good reproduction picture image can be obtained. Further,since the signal inserted in the digital audio signal region is not asignal which only has a dc level, and sags can be reproduced.

According to a yet further aspect of the present invention, there isprovided a video signal recording and reproducing apparatus of the typewherein a video signal is FM modulated and a digital audio signal istime division multiplexed into a blanking period of the FM modulatedvideo signal and recorded and reproduced by means of a pair of heads,comprising region signal generating means for identifying, uponreproduction, a region of a digital audio signal in a reproductionsignal reproduced by either of the heads and generating a control signalrepresentative of such region of the digital audio signal, a pair ofdelaying means for delaying reproduction signals from the heads by afixed period of time, first changing over means for selecting one of areproduction signal from one of the heads and an output of one of thedelaying means connected to the other of the heads in accordance with anoutput signal of the region signal generating means, second changingover means for selecting one of a reproduction signal from the other ofthe heads and an output of the other of the delaying means connected tothe one of the heads in accordance with an output signal of the regionsignal generating means, and a head changing over circuit for selectingone of outputs of the first and second changing over means in accordancewith reproducing operation of the heads.

With the video signal recording and reproducing apparatus, reproductionsignals from the heads and signals obtained by delaying the reproductionsignals by a fixed period of time are selectively transmitted inaccordance with a digital region signal representative of a digitalaudio signal region by the first and second changing over means, and oneof outputs of the first and second changing over means is selected inaccordance with reproducing operation of the heads by the head changingover circuit and then FM demodulated. Consequently, a signal in thedigital audio signal region of the reproduction video signal is replacedby a reproduction video signal of a preceding field. Accordingly,synchronizing separation of a reproduction video signal can be performedaccurately, which assures a normal operation of a clamp circuit.Consequently, a good reproduction picture image can be obtained.Further, since the signal inserted in the digital audio signal region isnot a signal which only has a dc level, and sags can be reproduced.

The above and other objects, features and advantages of the presentinvention will become apparent from the following description and theappended claims, taken in conjunction with the accompanying drawings inwhich like parts or elements are denoted by like reference characters.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a video tape recorder showing a firstpreferred embodiment of the present invention;

FIG. 2 is a waveform diagram showing an output waveform of areproduction video signal of the video tape recorder of FIG. 1;

FIG. 3 is a circuit diagram showing details of a clip circuit of thevideo tape recorder of FIG. 1;

FIG. 4 is a waveform diagram illustrating operation of the clip circuitof FIG. 3;

FIG. 5 is a block diagram of a magnetic recording and reproducingapparatus showing a second preferred embodiment of the presentinvention;

FIG. 6 is a similar view but showing a modification to the magneticrecording and reproducing apparatus of FIG. 5;

FIG. 7 is a similar view but showing another modification to themagnetic recording and reproducing apparatus of FIG. 5;

FIG. 8 is a waveform diagram showing a waveform of an outputreproduction video signal of the magnetic recording and reproducingapparatus of FIG. 5;

FIG. 9 is a waveform diagram illustrating operation of a PCM regionsignal generator and a switch circuit of the magnetic recording andreproducing apparatus of FIG. 5;

FIG. 10 is a waveform diagram showing a waveform of an alternativeoutput reproduction video signal of the magnetic recording andreproducing apparatus of FIG. 5;

FIG. 11 is a block diagram of another magnetic recording and reproducingapparatus showing a third preferred embodiment of the present invention;

FIG. 12 is a waveform diagram showing a waveform of an outputreproduction video signal of the magnetic recording and reproducingapparatus of FIG. 11;

FIGS. 13a and 13b are circuit diagrams showing a white clip circuit anda pedestal clip circuit, respectively, of the magnetic recording andreproducing apparatus of FIG. 11;

FIG. 14 is a waveform diagram illustrating operation of the white clipcircuit and pedestal clip circuit of FIGS. 13a and 13b;

FIG. 15 is a block diagram showing a modification to the magneticrecording and reproducing apparatus of FIG. 11;

FIG. 16 is a similar view but showing a modification to the modifiedmagnetic recording and reproducing apparatus of FIG. 15;

FIG. 17 is a waveform diagram showing a waveform of an outputreproduction video signal of the modified magnetic recording andreproducing apparatus shown in FIG. 15 or 16;

FIG. 18 is a waveform diagram illustrating operation of a PCM regionsignal generator and a switch circuit of the modified magnetic recordingand reproducing apparatus shown in FIG. 15 or 16;

FIG. 19 is a block diagram showing another modification to the magneticrecording and reproducing apparatus of FIG. 11;

FIG. 20 is a waveform diagram illustrating operation of a PCM regionsignal generator, a delay element and a switch circuit of the modifiedmagnetic recording and reproducing apparatus of FIG. 19;

FIG. 21 is a block diagram showing a further modification to themagnetic recording and reproducing apparatus of FIG. 11;

FIG. 22 is a waveform diagram illustrating operation of a PCM regionsignal generator, a delay element and a switch circuit of the modifiedmagnetic recording and reproducing apparatus of FIG. 21;

FIG. 23 is a block diagram of a further magnetic recording andreproducing apparatus showing a fourth preferred embodiment of thepresent invention;

FIG. 24 is a similar view but showing a modification to the magneticrecording and reproducing apparatus of FIG. 23;

FIG. 25 is a similar view but showing another modification to themagnetic recording and reproducing apparatus of FIG. 23;

FIG. 26 is a waveform diagram showing a waveform of vertical blankingdata generated by a vertical blanking data generator of the magneticrecording and reproducing apparatus shown in FIG. 23, 24 or 25;

FIG. 27 is a similar view but showing an output waveform of areproduction video signal of the magnetic recording and reproducingapparatus of FIG. 23, 24 or 25;

FIG. 28 is a waveform diagram illustrating operation of a PCM regionsignal generator and a switch circuit of the magnetic recording andreproducing apparatus of FIG. 23;

FIG. 29 is a block diagram of a still further magnetic recording andreproducing apparatus showing a fifth preferred embodiment of thepresent invention;

FIG. 30 is a waveform diagram illustrating operation of the magneticrecording and reproducing apparatus of FIG. 29;

FIG. 31 is a block diagram showing a modification to the magneticrecording and reproducing apparatus of FIG. 29;

FIG. 32 is a time chart illustrating addition of a PCM audio signal to afirst or last end of each of tracks on which a video signal is recorded;

FIG. 33 is a time chart illustrating alternative operation of themagnetic recording and reproducing apparatus of FIG. 29;

FIG. 34 is a similar view but illustrating another alternative operationof the magnetic recording and reproducing apparatus of FIG. 29;

FIG. 35 is a time chart illustrating a further alternative operation ofthe magnetic recording and reproducing apparatus of FIG. 29;

FIG. 36 is a block diagram showing another modification to the magneticrecording and reproducing apparatus of FIG. 29;

FIG. 37 is a time chart illustrating operation of the modified magneticrecording and reproducing apparatus of FIG. 36;

FIG. 38 is a block diagram of a yet further magnetic recording andreproducing apparatus showing a sixth preferred embodiment of thepresent invention;

FIG. 39 is a waveform diagram showing a waveform of an outputreproduction video signal after FM demodulation of the magneticrecording and reproducing apparatus of FIG. 38;

FIG. 40 is a waveform diagram illustrating operation of a PCM regionsignal generator, a delay element and a switch circuit of the magneticrecording and reproducing apparatus of FIG. 38;

FIG. 41 is a similar view but illustrating alternative operation of thePCM region signal generator, delay element and switch circuit of themagnetic recording and reproducing apparatus of FIG. 38;

FIG. 42 is a block diagram showing a modification to the magneticrecording and reproducing apparatus of FIG. 38;

FIG. 43 is a similar view but showing another modification to themagnetic recording and reproducing apparatus of FIG. 38;

FIG. 44 is a similar view but showing a modification to the modifiedmagnetic recording and reproducing apparatus of FIG. 43;

FIG. 45 is a similar view but showing a further modification to themagnetic recording and reproducing apparatus of FIG. 38;

FIG. 46 is a waveform diagram illustrating operation of a PCM regionsignal generator, an FM signal generator and a switch circuit of themagnetic recording and reproducing apparatus of FIG. 45;

FIG. 47 is a waveform diagram illustrating operation of the FM signalgenerator and switch circuit of the magnetic recording and reproducingapparatus of FIG. 45 when an FM video signal and a PCM audio signal of areproduction signal are separated and processed;

FIG. 48 is a block diagram showing a modification to the modifiedmagnetic recording and reproducing apparatus of FIG. 45;

FIG. 49 is a block diagram showing a still further modification to themagnetic recording and reproducing apparatus of FIG. 38;

FIG. 50 is a waveform diagram illustrating operation of a PCM regionsignal generator, delay elements and switch circuits of the magneticrecording and reproducing apparatus of FIG. 49;

FIG. 51 is a waveform diagram illustrating operation of the delayelements and switch circuits of the magnetic recording and reproducingapparatus of FIG. 49 when an FM video signal and a PCM audio signal of areproduction signal are separated and processed;

FIG. 52 is a block diagram showing a conventional magnetic recording andreproducing apparatus;

FIG. 53 is a waveform diagram illustrating time division multiplexing ofa PCM audio signal into a blanking period of an FM video signal;

FIG. 54 is a waveform diagram showing a waveform an output signal afterFM demodulation of the conventional magnetic recording and reproducingapparatus of FIG. 52;

FIG. 55 is a block diagram showing another conventional magneticrecording and reproducing apparatus;

FIG. 56 is a waveform diagram showing a recording video signal beforeinputting to an FM modulator of the conventional magnetic recording andreproducing apparatus;

FIG. 57 is a waveform diagram illustrating operation of the magneticrecording and reproducing apparatus of FIG. 55 when an FM video signaland a PCM audio signal of a reproduction signal are separated and thereproduction FM video signal is FM demodulated;

FIG. 58 is a waveform diagram illustrating time division multiplexing ofa PCM audio signal into a segment blanking period of an FM video signalin two segment recording;

FIG. 59 is a block diagram showing a further conventional magneticrecording and reproducing apparatus;

FIG. 60 is a diagrammatic representation showing a rotary drum as viewedfrom above;

FIG. 61 is a diagrammatic view showing a record pattern on a magnetictape:

FIG. 62 is a waveform diagram illustrating operation of a head changingover circuit of the conventional magnetic recording and reproducingapparatus of FIG. 59;

FIG. 63 is a waveform diagram illustrating operation of a reproductionequalizer and a limiter of the conventional magnetic recording andreproducing apparatus of FIG. 59;

FIG. 64 is a diagram showing a frequency characteristic of thereproduction equalizer of the conventional magnetic recording andreproducing apparatus of FIG. 59; and

FIG. 65 is a diagram showing an FM video signal band and a PCM audiosignal band of the conventional magnetic recording and reproducingapparatus of FIG. 59 upon reproduction.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring first to FIG. 1, there is shown a magnetic recording andreproducing apparatus to which the present invention is applied. Themagnetic recording and reproducing apparatus shown is a video taperecorder and includes a recording system including a pre-emphasiscircuit 10 for emphasizing high frequency components of a video signal,an FM modulator 11 for FM modulating a video signal, a PCM encoder 12for processing an input audio signal by shuffling, addition of an errorcorrection code and so forth and time base compressing the thusprocessed audio signal to allow an audio signal for one field period tobe inserted into a vertical blanking period of an FM video signal to PCMmodulate the audio signal, a pair of changing over switches 13 and 14for alternatively selecting, upon recording, an FM modulated videosignal and a PCM modulated audio signal, an adder 15 for adding an FMmodulated video signal and a PCM modulated audio signal outputted fromthe changing over switches 13 and 14, respectively, a recordingamplifier 16 for amplifying an output signal of the adder 15, and arecording video head 17 in the form of a rotary head for recording anoutput signal of the recording amplifier 16 onto a magnetic tape 200 asa magnetic record medium. The recording system of the magnetic recordingand reproducing system is similar to that of the conventional magneticrecording and reproducing apparatus described hereinabove with referenceto FIG. 52.

The magnetic recording and reproducing apparatus further includes areproducing system including a reproducing video head 18 in the form ofa rotary head, a reproduction amplifier 19 for amplifying an outputsignal of the reproducing video head 18, a reproduction equalizer 20 forcompensating for a frequency characteristic of a reproduction FM videosignal, an FM demodulator 21 for demodulating a reproduction FM videosignal, and a de-emphasis circuit 22 having a reverse characteristic tothat of the pre-emphasis circuit 10, similarly to the reproducing systemof the conventional magnetic recording and reproducing apparatusdescribed hereinabove with reference to FIG. 52.

The reproducing system of the magnetic recording and reproducingapparatus further includes a PCM decoder 34 for decoding an outputsignal of the reproduction amplifier 19, that is, for detecting a PCMaudio signal for one field inserted in a vertical blanking period of areproduction signal and processing the detected PCM audio signal byerror correction, de-shuffling and so forth to restore an original audiosignal, similarly to the PCM decoder 23 of the conventional magneticrecording and reproducing apparatus of FIG. 52. The PCM decoder 34,however, includes therein a PCM region signal generator 35 whichaccurately discriminates a region of a PCM modulated audio signal in areproduction signal and generates a control signal representative of aPCM audio signal region. The reproducing system of the magneticrecording and reproducing apparatus further includes a clip circuit 36for clipping a lower end portion of a reproduction FM demodulated signalobtained by FM demodulation in a PCM audio signal region of areproduction signal of the reproduction video head 18 in accordance witha PCM region signal outputted from the PCM region signal generator 35 ofthe PCM decoder 34. Though not shown, the reproducing system may furtherinclude such clamp circuit, A/D converter, synchronizing separatorcircuit, reproduction signal processing circuit and D/A converter as inthe reproducing system of the magnetic recording and magnetic apparatusof FIG. 52.

The magnetic recording and reproducing apparatus operates in thefollowing manner. In particular, an input video signal inputted, uponrecording, to the recording system by way of a video signal inputterminal 100 is first supplied to the pre-emphasis circuit 10, at whichhigh frequency components thereof are emphasized, and then to the FMmodulator 11, at which it is FM modulated to obtain an FM video signal.Meanwhile, an input audio signal is inputted to the recording system byway of an audio signal input terminal 101 and supplied to the PCMencoder 12, at which processing of shuffling, addition of an errorcorrection code and so forth is performed therefor and then time basecompressing processing is performed for the thus processed audio signalin order to allow the audio signal for one field period to be laterinserted into a fixed portion of a vertical blanking period of the FMvideo signal. The PCM encoder 12 outputs the thus PCM modulated audiosignal therefrom. The PCM modulated audio signal from the PCM encoder 12and the FM modulated video signal from the FM modulator 11 are thenalternatively selected by the switches 13 and 14, that is, selectivelytransmitted to the adder 15 in accordance with a suitable change overoperation of the switches 13 and 14 so that they are added to each othersuch that the PCM audio signal may be recorded in a recording area whichis provided at a fixed portion of a vertical blanking period of an FMmodulated video signal as seen in FIG. 54 thereby to produce a recordingsignal. The recording signal is supplied from the adder 15 to therecording amplifier 16, at which the FM video signal and the PCM audiosignal thereof are amplified. The composite recording signal of the FMvideo signal and the PCM audio signal is then recorded onto a magnetictape 200 by means of the recording video head 17.

On the other hand, upon reproduction, such FM video signal and PCM audiosignal recorded in a mixed condition on the magnetic tape 200 arereproduced from the magnetic tape 200 by means of the reproducing videohead 18 and amplified as a reproduction signal by the reproductionamplifier 19. The thus amplified reproduction signal is transmitted tothe reproduction equalizer 20 and also to the PCM decoder 34. At the PCMdecoder 34, a PCM audio signal for one field inserted in a verticalblanking period of such reproduction signal is detected and thenprocessed by time base elongation, error correction, de-shuffling and soforth to restore an original audio signal. The thus restored originalaudio signal by the PCM decoder 34 is outputted as a reproduction outputaudio signal of the reproducing system by way of a reproduction audiosignal output terminal 103.

In the meantime, the reproduction equalizer 20 compensates for afrequency characteristic of the reproduction FM video signal in thereproduction signal received from the reproduction amplifier 19, and anoutput of the reproduction equalizer 20 is then FM demodulated by the FMdemodulator 21. The FM demodulated video signal is inputted to thede-emphasis circuit 22, at which high frequency components thereof,which were emphasized by the pre-emphasis circuit 10 upon recording, arede-emphasized to restore an original video signal.

The operation of the magnetic recording and reproducing apparatusdescribed above is similar to that of the conventional magneticrecording and reproducing apparatus of FIG. 52. By the way, since a PCMaudio signal is added, upon recording, into a predetermined portion of ablanking period of an FM modulated video signal in response to asuitable change over operation of the change over switches 13 and 14 andthen, upon reproduction, a reproduction FM video signal and a PCM audiosignal mixed with such reproduction FM video signal are FM demodulatedas they are, such reproduction video signal including such reproductionFM video signal and PCM audio signal presents such an output signalwaveform as shown in FIG. 54 as if it includes noises in a PCM audiosignal region.

Thus, in the video tape recorder of the present invention, areproduction FM demodulated signal outputted from the de-emphasiscircuit 22 is inputted by way of a reproduction FM demodulated signalinput terminal 104 (FIG. 3) to the clip circuit 36. At the clip circuit36, the clip level thereof is controlled in accordance with a PCM regionsignal outputted from the PCM region signal generator 35 andrepresentative of a PCM audio signal region. In particular, the clipcircuit 36 clips lower ends of noises in a PCM audio signal region of areproduction FM demodulated signal at a level substantially equal to apedestal level. Consequently, the output reproduction video signal ofthe clip circuit 36 exhibits such an output waveform as shown in FIG. 2.

Here, the PCM region signal generator 35 in the PCM decoder 34 generatesa PCM region signal by such construction that an end timing of a PCMaudio signal region of a reproduction signal is detected and a startingtime of a next PCM audio signal region is predicted from a result ofsuch detection. Such PCM region signal generator 35, which is capable ofgenerating a PCM region signal representative of a PCM audio signalregion, can be constructed making use of a suitable known technique.

Meanwhile, the clip circuit 36 may be constructed in such a manner as,for example, shown in FIG. 3. The clip circuit 36 shown in FIG. 3includes a transistor 361, resistors 362, 363 and 364 and so forth.

The PCM region signal generator 35 generates such a PCM region signalpulse, for example, which presents a low level in a PCM audio signalregion but presents a high level in a video signal region as shown by awaveform (b) in FIG. 4. Such PCM region signal pulse is inputted to theclip circuit 36 by way of a PCM region signal input terminal 105 (FIG.3). Here in the clip circuit 36, since the PCM region signal pulse fromthe PCM region signal input terminal 105 presents a low level in a PCMaudio signal region, the transistor 361 does not conduct. Consequently,the clip level of the clip circuit 36 depends upon the resistors 362 and363. On the other hand, in a video signal region, the PCM region signalpulse from the PCM region signal input terminal 105 presents a highlevel, and consequently, the transistor 361 conducts. Consequently, theclip level of the clip circuit 36 depends upon the resistors 362, 363and 364.

Accordingly, the clip level of the clip circuit 36 is set, in a PCMaudio signal region, to a pedestal level as seen from a waveform (a) ofFIG. 4 while the clip level is set, in a video signal region, to asynchronization end level. In particular, the resistors 362, 363 and 364are set to a resistance value such that, in a video signal region, asignal is clipped substantially at a synchronization end level similarlyas in a case, for example, wherein a signal which has been dropped belowa synchronization end level is to be clipped so as to allow the signalto be inputted to a reproduction analog to digital converter. Where suchconstruction is employed, a reproduction FM demodulated signal outputtedfrom the de-emphasis circuit 22 is inputted to the clip circuit 36 byway of the reproduction FM demodulated signal input terminal 104 so thatlower ends of noises in a PCM audio signal region of the FM demodulatedoutput signal in the reproduction signal can be clipped.

Thus, since the clip circuit 36 can accurately perform synchronizationseparation of a video signal, a stabilized reproduction video signal canbe outputted from a reproduction video signal output terminal 106. Areproduction video signal obtained in this manner by the clip circuit 36is outputted from a reproduction video signal output terminal 102 of thereproducing system shown in FIG. 1.

It is to be noted that, while the magnetic recording and reproducingapparatus of FIG. 1 is constructed such that a PCM audio signal isrecorded into a fixed portion of a vertical blanking period of an FMvideo signal in accordance with a suitable change over operation of thechange over switches 13 and 14, a PCM audio signal may otherwise berecorded into a horizontal blanking period or into vertical andhorizontal blanking periods. In any case, similar effects to those ofthe magnetic recording and reproducing apparatus of FIG. 1 describedabove can be attained if a magnetic recording and reproducing apparatusincludes a PCM region signal generator which accurately identifies aregion of a PCM modulated audio signal in a reproduction signal read outupon reproduction by a rotary head and generates a control signalrepresentative of a PCM audio signal region and a clip circuit the cliplevel of which can be controlled, in accordance with such PCM regionsignal outputted from the PCM region signal generator, in a PCM audiosignal region of a reproduction FM demodulated signal obtained by FMdemodulation of a reproduction signal from the rotary head so that lowerends of noises in a PCM audio signal region of a reproduction FMdemodulated signal can be clipped at a level substantially equal to apedestal level.

Referring now to FIG. 5, there is shown a magnetic recording andreproducing apparatus according to a second preferred embodiment of thepresent invention. The magnetic recording and reproducing apparatusshown includes a recording system which is similar to the recordingsystem of the magnetic recording and reproducing apparatus of the firstembodiment described hereinabove with reference to FIG. 1. The magneticrecording and reproducing apparatus further includes a reproducingsystem which includes a reproducing video head 18, a reproductionamplifier 19, a reproduction equalizer 20, an FM demodulator 21, ade-emphasis circuit 22 and a PCM decoder 34 including a PCM regionsignal generator 35 therein, similarly to the reproducing system of themagnetic recording and reproducing apparatus of FIG. 1. The reproducingsystem of the magnetic recording and reproducing apparatus furtherincludes a level signal generator 37 for generating a signal having afixed level with respect to a video signal, and a switch circuit 38 forreceiving a reproduction video signal outputted from the FM demodulator21 and an output of the level signal generator 37 and selecting one ofthe received signals in response to a PCM region signal received fromthe PCM region signal generator 35. An output of the switch circuit 38is inputted to the de-emphasis circuit 22, from which it is outputted asa reproduction video signal.

The magnetic recording and reproducing apparatus operates in thefollowing manner. In particular, the recording system operates in asimilar manner to the recording system of the magnetic recording andreproducing apparatus of FIG. 1. Meanwhile, in the reproducing system,the components 18, 19, 20, 21, 34 and 35 thereof operate in a similarmanner to those of the reproducing system of the magnetic recording andreproducing apparatus of FIG. 1 described hereinabove.

Accordingly, similarly as described hereinabove, if, upon reproduction,a reproduction FM video signal and a PCM audio signal mixed with suchreproduction FM video signal are FM demodulated as they are by the FMdemodulator 21 and passed through the de-emphasis circuit 22, then thereproduction video signal from the de-emphasis circuit 22 will presentsuch an output signal waveform as shown in FIG. 54 as if it includesnoises in a PCM audio signal region.

Thus, in the present magnetic recording and reproducing apparatus, thelevel signal generator 37 generates such a fixed level signal that willprovide, for example, a gray level when it is de-emphasized by thede-emphasis circuit 22 as seen from a waveform (a) in FIG. 9, and anoutput of the level signal generator 37 and an output of the FMdemodulator 21 are inputted to the switch circuit 38, which operates inresponse to a PCM region signal representative of a PCM audio signalregion, so that they may be selectively outputted from the switchcircuit 38. Such PCM region signal is generated by the PCM region signalgenerator 35 provided in the PCM decoder 34 and is transmitted to theswitch circuit 23.

If the PCM region signal generator 35 develops a pulse which presents,for example, a low level in a PCM audio signal region and a high levelin a video signal region as shown by a waveform (b) in FIG. 9 and isinputted to the switch circuit 38, the switch circuit 38 selects areproduction FM demodulated signal transmitted thereto from the FMdemodulator 21 in a period of a video signal region in which the pulsepresents a high level, but selects an output of the level signalgenerator 37 in a period of a PCM audio signal region in which the pulsepresents a low level. Then, an output of the switch circuit 38 isinputted to the de-emphasis circuit 22, at which high frequencycomponents, which were emphasized by the pre-emphasis circuit 10 in therecording system, are de-emphasized. Consequently, a reproduction videosignal wherein high frequency noises have been reduced is obtained.Further, such a fixed level signal at a gray level as shown by thewaveform (a) of FIG. 9 is obtained in a PCM audio signal region.

Since a signal of an FM demodulated output of a reproduction signal in aPCM audio signal region can be made as a fixed gray level signal,synchronization separation of a video signal can be performed accuratelyand a stabilized reproduction video signal can be obtained.

Referring now to FIG. 6, there is shown a modification to the magneticrecording and reproducing apparatus of FIG. 5 described above. Thepresent magnetic recording and reproducing apparatus is modified suchthat the switch circuit 38 is provided at a next stage to thede-emphasis circuit 22. Consequently, a fixed level signal outputtedfrom the level signal generator 37 and a reproduction FM demodulatedsignal outputted from the de-emphasis circuit 22 are alternativelyselected by the switch circuit 38 which is controlled in accordance witha PCM region signal outputted from the PCM region signal generator 35.Also with the modified magnetic recording and reproducing apparatus,such a fixed level signal of a gray level as shown by the waveform (a)of FIG. 9 can be obtained.

Referring now to FIG. 7, there is shown another modification to themagnetic recording and reproducing apparatus of FIG. 5. The presentmagnetic recording and reproducing apparatus is modified such that oneof a fixed frequency signal outputted from a fixed frequency signalgenerator 39 and a reproduction signal which is outputted from thereproduction equalizer 20 and is not yet in an FM demodulated conditionis selected by the switch circuit 38 which is controlled in accordancewith a PCM region signal received from the PCM region signal generator35 in the PCM decoder 34. Here, the fixed frequency signal generator 39generates a signal of such a frequency with which a signal of a graylevel may be obtained by FM demodulation thereof. The signal selected bythe switch circuit 38 is subsequently processed successively by the FMdemodulator 21 and de-emphasis circuit 22 to obtain a reproduction videosignal which presents a fixed gray level in a PCM audio signal region.

The modified magnetic recording and reproducing apparatus of FIGS. 6 and7 described above are advantageous similarly to the magnetic recordingand reproducing apparatus of FIG. 5.

It is to be noted that, while any of the magnetic recording andreproducing apparatus of FIGS. 5 to 7 is constructed such that a fixedlevel signal or a fixed frequency signal from which a signal of a graylevel will be obtained by de-emphasis thereof is generated by the levelsignal generator 37 or fixed frequency signal generator 39, such levelsignal generator 37 or fixed frequency signal generator 39 may otherwisegenerate a signal from which a signal of such a white level as shown bya waveform (b) in FIG. 10 or such a pedestal level as shown by anotherwaveform (c) in FIG. 10 is obtained. Or else, similar effects can beachieved even where such level signal generator 37 or fixed frequencysignal generator 39 generates a signal from which a signal having afixed level between a pedestal level and a white level of a video signalin a PCM audio signal region of a reproduction video signal isobtained..

Further, while any of the magnetic recording and reproducing apparatusof FIGS. 5 to 7 is constructed such that the PCM region signal generator35 generates a pulse which presents a high level in a video signalregion but presents a low level in a PCM audio signal region, it mayotherwise be constructed such that the PCM region signal generator 35generates a pulse having an inverted phase such that it presents a lowlevel in a video signal region but presents a high level in a PCM audiosignal region while the switch circuit 38 is constructed such that itmay select a suitable signal in either of a video signal region and aPCM audio signal region. Also with the alternative construction, similareffects to those of the magnetic recording and reproducing apparatus ofFIGS. 5 to 7 described above can be achieved.

Further, while any of the magnetic recording and reproducing apparatusof FIGS. 5 to 7 is constructed such that a PCM audio signal is insertedinto a fixed portion of a vertical blanking period of an FM modulatedvideo signals a PCM audio signal may be inserted in some other way intoan FM modulated video signal. For example, a PCM audio signal may beinserted into a horizontal blanking period of an FM modulated videosignal. Or else, in a magnetic recording and reproducing apparatus ofthe type wherein a video signal is separated into a plurality ofsegments and recorded onto and reproduced from a magnetic tape, a PCMaudio signal may be inserted into a segment blanking period. In anycase, if a PCM region signal generator can, upon reproduction, identifya PCM audio signal region of a reproduction signal and generate acontrolling signal representative of such region, then similar effectsto those of the magnetic recording and reproducing apparatus of FIGS. 5to 7 can be attained.

Referring now to FIG. 11, there is shown a magnetic recording andreproducing apparatus according to a third preferred embodiment of thepresent invention. The magnetic recording and reproducing apparatusshown includes a recording system which is similar to the recordingsystem of the magnetic recording and reproducing apparatus of the firstembodiment described hereinabove with reference to FIG. 1. The magneticrecording and reproducing apparatus further includes a reproducingsystem which includes a reproducing video head 18, a reproductionamplifier 19, a reproduction equalizer 20, an FM demodulator 21, ade-emphasis circuit 22 and a PCM decoder 34 including a PCM regionsignal generator 35 therein, similarly to the reproducing system of themagnetic recording and reproducing apparatus of FIG. 1. The magneticrecording and reproducing apparatus further includes a clamp circuit 24,an analog to digital (A/D) converter 25 for converting a reproductionvideo signal from an analog signal into a digital signal, asynchronizing separator circuit 26 for separating a synchronizing signalfrom a reproduction video signal, a reproduction signal processingcircuit 27 for processing a reproduction signal by time base correction,dropout compensation and so forth in accordance with a synchronizingseparation signal from the synchronizing separator circuit 26, and adigital to analog (D/A) converter 28, similarly to the conventionalmagnetic recording and reproducing apparatus described hereinabove withreference to FIG. 52.

The reproducing system of the magnetic recording and reproducingapparatus further includes a PCM clip circuit 41 for clipping upper endportions and lower end portions of noise in a PCM audio signal region ofan FM demodulated reproduction video signal in accordance with a PCMregion signal received from the PCM region signal generator 35 in thePCM decoder 34. The PCM clip circuit 41 includes a white clip circuit 42for clipping upper end portions of noise at a white level and a pedestalclip circuit 43 for clipping lower end portions of noise at a pedestallevel.

The magnetic recording and reproducing apparatus operates in thefollowing manner. In particular, the recording system operates in asimilar manner to the recording system of the magnetic recording andreproducing apparatus of FIG. 1. Meanwhile, in the reproducing system,the components 18, 19, 20, 21, 22, 34 and 35 thereof operate in asimilar manner to those of the reproducing system of the magneticrecording and reproducing apparatus of FIG. 1 described hereinabove.

Accordingly, similarly as described hereinabove, if, upon reproduction,a reproduction FM video signal and a PCM audio signal mixed with suchreproduction FM video signal are FM demodulated as they are by the FMdemodulator 21 and then passed through the de-emphasis circuit 22, thereproduction video signal from the de-emphasis circuit 22 will presentsuch an output signal waveform as shown in FIG. 54 as if it includesnoises in a PCM audio signal region.

Thus, a reproduction video signal outputted from the de-emphasis circuit22 is inputted to the PCM clip circuit 41 the clip level of which can becontrolled in accordance with a PCM region signal representative of aPCM audio signal region. Such PCM region signal is generated by the PCMregion signal generator 35 in the PCM decoder 34 and is transmitted tothe PCM clip circuit 41, and the PCM clip circuit 41 clips upper endportions of noise in a PCM audio signal region of the reproduction videosignal outputted from the de-emphasis circuit 22 at a white level or soand then clips lower end portions of such noise at a pedestal level orso as seen from FIG. 12.

As described above, the PCM clip circuit 41 includes the white clipcircuit 42 for clipping a portion of a reproduction video signal higherthan a white level in a PCM audio signal region of such reproductionvideo signal and the pedestal clip circuit 43 for clipping anotherportion of such reproduction video signal below a pedestal level. Thewhite clip circuit 42 and pedestal clip circuit 43 may be constructed insuch a manner as shown, for example, in FIGS. 12a and 12b, respectively.

Thus, if the PCM region signal generator 35 in the PCM decoder 34generates, for example, such a pulse which presents a low level in a PCMaudio signal region but presents a high level in a video signal regionas shown by a waveform (e) in FIG. 14 and delivers it to the PCM clipcircuit 41, in the white clip circuit 42 shown in FIG. 13a in the PCMclip circuit 41, a transistor Tr₁ does not conduct but anothertransistor Tr₂ conducts in a PCM audio signal region, and consequently,the clip level of the white clip circuit 42 depends upon resistances ofresistors R₁, R₂ and R₃. On the other hand, in a video signal region,the transistor Tr₁ conducts but the transistor Tr₂ does not conduct, andconsequently, the clip level depends upon the resistances of theresistors R₁ and R₂. Accordingly, the resistors R₁, R₂ and R₃ are set toa resistance value such that the clip level in a PCM audio signal regionmay be equal to a white level b shown in FIG. 14 but the clip level in avideo signal region may be a level a higher than such white level sothat it may have no influence on a level of a video signal.

On the other hand, in the pedestal clip circuit 43 shown in FIG. 13b inthe PCM clip circuit 41, a transistor Tr₃ does not conduct, andconsequently, the clip level of the pedestal clip circuit 43 dependsupon resistances of resistors R₄ and R₅. On the other hand, in a videosignal region, the transistor Tr₃ conducts, the clip level depends uponthe resistances of the resistors R₄, R₅ and R₆. Accordingly, theresistors R₄, R₅ and R₆ are set to a resistance value such that the cliplevel in a PCM audio signal region may be equal to a white level c shownin FIG. 14 but the clip level in a video signal region may be a levelsubstantially equal to a level of an end of a synchronization signal sothat it may clip a signal which has been dropped below a synchronizationsignal end level so as to allow the signal to be inputted, for example,to the reproduction analog to digital converter 25.

Where such construction is employed for the PCM clip circuit 41, upperend portions and lower end portions of noise of an FM demodulatedreproduction video signal in a PCM audio signal region can be clipped,and consequently, synchronization separation of a reproduction videosignal can be performed accurately. Consequently, the clamp circuit 24at a next stage can operate normally, and sags can be reduced.

The reproduction video signal outputted from the PCM clip circuit 41 isthen inputted to the clamp circuit 24, at which it is clamped at apredetermined dc voltage level. The thus clamped reproduction videosignal from the clamp circuit 24 is then converted from an analog signalto a digital signal by the A/D converter 25 and then transmitted to thereproduction signal processing circuit 27. The clamped reproductionvideo signal is also transmitted to the synchronizing separator circuit26, at which a synchronizing signal is separated. The reproductionsignal processing circuit 27 performs reproduction signal processingsuch as time base correction and dropout compensation of thereproduction video signal from the A/D converter 25 in accordance with asynchronizing separation signal outputted from the synchronizingseparator circuit 26, and an output reproduction video signal of thereproduction signal processing circuit 27 is converted from a digitalsignal into an analog signal by the D/A converter 28 and outputted as areproduction output video signal of the reproducing system.Consequently, a good reproduction output video signal can be obtainedfrom the reproducing system of the magnetic recording and reproducingapparatus.

It is to be noted that, while the PCM clip circuit 41 is constructedfrom such white clip circuit 42 and pedestal clip circuit 43 as shown inFIGS. 13a and 13b, respectively, similar effects can be achieved if amagnetic recording and reproducing apparatus has such construction thatit comprises a PCM region signal generator for identifying, uponreproduction, a region of a PCM audio signal mixed in a reproductionsignal and generating a control signal representative of such PCM audiosignal region and a clip circuit having a clip level capable of beingcontrolled by such controlling signal, and upper end portions and lowerend portions of noise of a reproduction video signal in a PCM audiosignal region are clipped at such levels at which sags can be reducedand synchronizing separation of a reproduction video signal can beperformed accurately.

Further, while a PCM audio signal is inserted into a vertical blankingperiod of an FM modulated video signal in accordance with a suitablechanging over operation of the switches 13 and 14 in the magneticrecording and reproducing apparatus of FIG. 11, it may be inserted insome other way into an FM modulated video signal. For example, a PCMaudio signal may be inserted in several separate parts into a horizontalblanking period of an FM modulated video signal. Further, also in thecase wherein a PCM audio signal for one field is inserted in severalparts into a segment blanking period and a vertical blanking period ofan FM modulated video signal and recorded onto and then reproduced froma magnetic tape in a video tape recorder of the type wherein a videosignal for one field is separated into a plurality of segments andrecorded onto and reproduced from a magnetic tape, if such constructionis employed that a region of a PCM audio signal in a reproduction signalis identified to generate a control signal representative of such PCMaudio signal region and it comprises a clip circuit having a clip levelcapable of being controlled by such control signal so that upper endportions and lower end portions of noise of a reproduction video signalin a PCM audio signal region can be clipped at such levels at which sagscan be reduced and synchronizing separation of a reproduction videosignal can be performed accurately, then similar effects can beexhibited with such a recording format wherein a PCM audio signal isrecorded in a segment blanking period.

Further, while a PCM audio signal mixed in a reproduction FM videosignal is FM demodulated as it is as a reproduction signal uponreproduction in the magnetic recording and reproducing apparatus of FIG.11, even with a possible alternate construction wherein an FM videosignal and a PCM audio signal of a reproduction signal are separatedfrom each other before such FM video signal is FM demodulated, areproduction video signal after FM demodulation will include such noisein a PCM audio signal region as seen in FIG. 54. Accordingly, if suchconstruction is employed similarly as in the magnetic recording andreproducing apparatus of FIG. 11 that it comprises a clip circuit havinga clip level capable of being controlled in accordance with a PCM regionsignal outputted from a PCM region signal generator so that upper endportions and lower end portions of noise in a PCM audio signal region ofa reproduction video signal after FM demodulation can be clipped at suchlevels at which sags can be reduced and synchronizing separation of areproduction video signal can be performed accurately, then similareffects to those of the magnetic recording and reproducing apparatus ofFIG. 11 can be attained.

Furthermore, while the PCM clip circuit 41 is constructed such that aninput signal thereto is processed first by the white clip circuit 42 andthen by the pedestal clip circuit 43, similar effects can be exhibitedwhere the PCM clip circuit 41 is constructed in a different manner suchthat an input signal thereto is processed first by the pedestal clipcircuit 43 and then by the white clip circuit 42.

Referring now to FIG. 15, there is shown a modification to the magneticrecording and reproducing apparatus of FIG. 11. The present magneticrecording and reproducing apparatus includes, in place of the PCMdecoder 34 including the PCM region signal generator 35 of the magneticrecording and reproducing apparatus of FIG. 11, a PCM decoder 46including a PCM region signal generator 47 which accurately identifies aPCM audio signal region of a reproduction signal and generates a PCMregion signal representative of such PCM audio signal region. Thepresent magnetic recording and reproducing apparatus further includes,in place of the PCM clip circuit 41 of the magnetic recording andreproducing apparatus of FIG. 11, a signal generator 48 for generating asine wave having, for example, a fixed frequency f and an amplitude Aand for overlapping the thus generated sine wave with a gray level of avideo signal, and a switch circuit 29 for selecting one of areproduction video signal outputted from the de-emphasis circuit 22 andan output of the signal generator 48 in accordance with a PCM regionsignal outputted from the PCM region signal generator 47.

The magnetic recording and reproducing apparatus operates in thefollowing manner. In particular, the recording system operates in asimilar manner to the recording system of the magnetic recording andreproducing apparatus of FIG. 11. Meanwhile, in the reproducing system,the components 18, 19, 20, 21, 22, 46 and 47 thereof operate in asimilar manner to the components 18, 19, 20, 21, 22, 34 and 35,respectively, of the reproducing system of the magnetic recording andreproducing apparatus of FIG. 11 described hereinabove.

Accordingly, similarly as described hereinabove, if, upon reproduction,a reproduction FM video signal and a PCM audio signal mixed with suchreproduction FM video signal are FM demodulated as they are by the FMdemodulator 21 and then passed through the de-emphasis circuit 22, thereproduction video signal from the de-emphasis circuit 22 will presentsuch an output signal waveform as shown in FIG. 54 as if it includesnoises in a PCM audio signal region.

Thus, a sine wave having, for example, a fixed frequency f and anamplitude A is generated and overlapped with a gray level of a videosignal by the signal generator 48, and one of an output of the signalgenerator 48 and a reproduction video signal outputted from thede-emphasis circuit 22 is selected by the switch circuit 49 which ischanged over in accordance with a PCM region signal received from thePCM region signal generator 47 in the PCM decoder 46 and representativeof a PCM audio signal region. Thus, such a signal as shown by a waveformin FIG. 17 is outputted from the switch circuit 49.

In particular, if the PCM region signal generator 47 in the PCM decoder46 generates, for example, such a pulse which presents a low level in aPCM audio signal region but presents a high level in a video signalregion as shown by a waveform (b) in FIG. 18 and delivers it to theswitch circuit 49, the switch circuit 49 selects, in a period of a videosignal region in which the pulse presents a high level, a reproductionvideo signal transmitted thereto from the de-emphasis circuit 22, butselects, in another period of a PCM audio signal region in which thepulse presents a low level, an output of the signal generator 48.Accordingly, a signal in a PCM audio signal region at the output of theswitch circuit 49 is such a sine wave signal overlapped with a graylevel and having a frequency f and an amplitude A as shown by a waveform(a) in FIG. 18.

Where such construction is employed, a signal in a PCM audio signalregion of an FM demodulated reproduction video signal can be formed as asine wave signal overlapped with a gray level and having the fixedfrequency f and the amplitude A, and consequently, synchronizationseparation of a reproduction video signal can be performed accuratelyand the clamp circuit 24 at a next stage can operate normally. Further,since a signal selected in a PCM audio signal region does not includeonly a dc level signal, sags can be reduced.

The reproduction video signal outputted from the switch circuit 49 isthen inputted to the clamp circuit 24, at which an end portion of asynchronizing signal thereof is clamped at a predetermined dc voltagelevel. The thus clamped reproduction video Signal from the clamp circuit24 is then converted from an analog signal to a digital signal by theA/D converter 25 and transmitted to the reproduction signal processingcircuit 27. The clamped reproduction video signal is transmitted also tothe synchronizing separator circuit 26, at which a synchronizing signalis separated. The reproduction signal processing circuit 27 performsreproduction signal processing such as time base correction and dropoutcompensation of the reproduction video signal from the A/D converter 25in accordance with a synchronizing separation signal outputted from thesynchronizing separator circuit 26, and an output reproduction videosignal of the reproduction signal processing circuit 27 is convertedfrom a digital signal into an analog signal by the D/A converter 28 andoutputted as a reproduction output video signal of the reproducingsystem. Consequently, a good reproduction output video signal can beobtained from the reproducing system of the magnetic recording andreproducing apparatus.

It is to be noted that, while the signal generator 48 generates a sinewave having a frequency f and an amplitude A and overlaps it with a graylevel, similar effects can be obtained by any other means whichgenerates a signal different from a fixed dc current level signal andhaving such a frequency at which sags can be reduced between a pedestallevel and a white level.

Further, while the magnetic recording and reproducing apparatus of FIG.15 is constructed such that the PCM region signal generator 47 generatesa pulse which presents a high level in a video signal region butpresents a low level in a PCM audio signal region, it may otherwise beconstructed such that the PCM region signal generator 47 generates apulse having an inverted phase such that it presents a low level in avideo signal region but presents a high level in a PCM audio signalregion while the switch circuit 49 is constructed such that it mayselect a reproduction FM demodulated signal from the de-emphasis circuit22 in a video signal region but select an output of the signal generator48 in a PCM audio signal region in accordance with a PCM region signaloutputted from the PCM region signal generator 47. Also with thealternative construction, similar effects to those of the magneticrecording and reproducing apparatus of FIG. 15 described above can beachieved.

Further, while a PCM audio signal is inserted into a vertical blankingperiod of an FM modulated video signal in accordance with a suitablechanging over operation of the switches 13 and 14 in the modifiedmagnetic recording and reproducing apparatus of FIG. 15, it may beinserted in some other way into an FM modulated video signal. Forexample, a PCM audio signal may be inserted in several separate partsinto a horizontal blanking period of an FM modulated video signal.Further, also in the case wherein a PCM audio signal for one field isinserted in several parts into a segment blanking period and a verticalblanking period of an FM modulated video signal and recorded onto andthen reproduced from a magnetic tape in a video tape recorder of thetype wherein a video signal for one field is separated into a pluralityof segments and recorded onto and reproduced from a magnetic tape, ifsuch construction is employed that a region of a PCM audio signal in areproduction signal is identified to generate a control signalrepresentative of such PCM audio signal region and the switch circuit 49selects, in accordance with such controlling signal, a reproduction FMdemodulated signal in a video signal region but selects an output of thesignal generator 48 in a PCM audio signal region, similar effects can beexhibited with such a recording format wherein a PCM audio signal isrecorded in a segment blanking period.

Further, while a PCM audio signal mixed in a reproduction FM videosignal is FM demodulated as it is as a reproduction signal uponreproduction in the modified magnetic recording and reproducingapparatus of FIG. 15, even with a possible alternate constructionwherein an FM video signal and a PCM audio signal in a reproductionsignal are separated from each other before such FM video signal is FMdemodulated, a reproduction video signal after FM demodulation willinclude such noise in a PCM audio signal region as seen in FIG. 54.Accordingly, if such construction is employed similarly as in themodified magnetic recording and reproducing apparatus of FIG. 15 thatthe switch circuit is changed over in accordance with a PCM regionsignal outputted from the PCM region signal generator.

Referring now to FIG. 16, there is shown a modification to the modifiedmagnetic recording and reproducing apparatus of FIG. 15. The presentmagnetic recording and reproducing apparatus is modified such that theswitch circuit 49 is interposed between the FM demodulator 21 and thede-emphasis circuit 22 such that it may select one of a reproduction FMdemodulated signal outputted from the FM demodulator 21 and an output ofa signal generator 50 similar to the signal generator 48 and supply thethus selected signal to the de-emphasis circuit 22. Similar effects tothose of the magnetic recording and reproducing apparatus of FIG. 15 canbe achieved also with the present modified magnetic recording andreproducing apparatus.

Referring now to FIG. 19, there is shown another modification to themagnetic recording and reproducing apparatus shown in FIG. 11. Thepresent magnetic recording and reproducing apparatus is modified suchthat it includes a PCM decoder 51 including a PCM region signalgenerator 52 therein in place of the PCM decoder 34 including the PCMregion signal generator 35 therein described above, and also includes aswitch circuit 53 and a delay element 54 for delaying a signal for onehorizontal scanning period (1 H) in place of the PCM clip circuit 41.The PCM region signal generator 52 detects a PCM audio signal for onefield period inserted in a vertical blanking period of a reproductionsignal., performs error correction and de-shuffling for the thusdetected PCM audio signal and outputs an original audio signal.

The magnetic recording and reproducing apparatus operates in thefollowing manner. In particular, the recording system operates in asimilar manner to the recording system of the magnetic recording andreproducing apparatus of FIG. 11. Meanwhile, in the reproducing system,the components 18, 19, 20, 21, 22, 51 and 52 thereof operate in asimilar manner to the components 18, 19, 20, 21, 22, 34 and 35,respectively, of the reproducing system of the magnetic recording andreproducing apparatus of FIG. 11 described hereinabove.

Accordingly, similarly as described hereinabove, if, upon reproduction,a reproduction FM video signal and a PCM audio signal mixed with suchreproduction FM video signal are FM demodulated as they are by the FMdemodulator 21 and then passed through the de-emphasis circuit 22, thenthe reproduction video signal from the de-emphasis circuit 22 willpresent such an output signal waveform as shown in FIG. 54 as if itincludes noises in a PCM audio signal region.

Thus, the reproduction video signal outputted from the de-emphasiscircuit 22 is transmitted to the switch circuit 53, by means of which asignal in a PCM audio signal region is replaced, as seen from a waveform(c) in FIG. 20, by another signal which includes a repetition of data ofa last line of a preceding field to the PCM audio signal region, inaccordance with a PCM region signal generated by and transmitted theretofrom the PCM region signal generator 52 in the PCM decoder 51.

In particular, if the PCM region signal generator 52 in the PCM decoder51 generates, for example, such a pulse which presents a low level in aPCM audio signal region but presents a high level in a video signalregion as shown by a waveform (b) in FIG. 20 and delivers it to theswitch circuit 53, then the switch circuit 53 selects, in a video signalregion in which the pulse presents a high level, a reproduction videosignal outputted from the de-emphasis circuit 22 and sends it as it isto the clamp circuit 24. On the other hand, in a period of a PCM audiosignal region in which the pulse presents a low level, the switchcircuit 53 is changed over so that an output of the delay element 54having a delay time equal to one horizontal scanning period is selected.Since data of a last line of a preceding field to the PCM audio signalregion are outputted from the delay element 54, a signal in the PCMaudio signal region presents such a waveform (c) as shown in FIG. 20wherein data of the last line of the preceding field to the PCM audiosignal region in which a PCM audio signal is inserted are repeated.

Since a reproduction video signal outputted from the switch circuit 53and inputted to the clamp circuit 24 has a PCM audio signal region inwhich last data of preceding field to a vertical blanking period inwhich a PCM audio signal is inserted are inserted repetitively as seenfrom the waveform (c) of FIG. 20, synchronization separation of areproduction video signal can be performed accurately and the clampcircuit 24 at a next stage can operate normally. Further, since asynchronizing signal is added also to a signal in a PCM audio signalregion, a signal in such PCM audio signal region can be clamped, andconsequently, sags can be reduced.

A reproduction video signal outputted from the switch circuit 53 is theninputted to the clamp circuit 24, at which an end portion of asynchronizing signal thereof is clamped at a predetermined dc voltagelevel. The thus clamped reproduction video signal from the clamp circuit24 is then converted from an analog signal to a digital signal by theA/D converter 25 and transmitted to the reproduction signal processingcircuit 27. The clamped reproduction video signal is transmitted also tothe synchronizing separator circuit 26, at which a synchronizing signalis separated. The reproduction signal processing circuit 27 performsreproduction signal processing such as time base correction and dropoutcompensation of the reproduction video signal from the A/D converter 25in accordance with a synchronizing separation signal outputted from thesynchronizing separator circuit 26, and an output reproduction videosignal of the reproduction signal processing circuit 27 is convertedfrom a digital signal into an analog signal by the D/A converter 28 andoutputted as a reproduction output video signal of the reproducingsystem. Consequently, a good reproduction output video signal can beobtained from the reproducing system of the magnetic recording andreproducing apparatus.

It is to be noted that, while the delay element 54 has a delay timeequal to 1 H, that is, one horizontal scanning period and data of a lastline of a preceding field to a vertical blanking period in which a PCMaudio signal is included are inserted repetitively into a PCM audiosignal region, it need not have such specific delay time, but may haveany other delay time which allows insertion of data several lines priorto a PCM audio signal region. Thus, similar effects can be exhibited ifa signal in a PCM audio signal region is replaced by data of severallines in a preceding field other than the PCM audio signal region.

Further, while the magnetic recording and reproducing apparatus of FIG.19 is constructed such that the PCM region signal generator 52 generatesa pulse which presents a high level in a video signal region butpresents a low level in a PCM audio signal region, it may otherwise beconstructed such that the PCM region signal generator 47 generates apulse having an inverted phase while a change over operation of theswitch circuit 53 is controlled in accordance with a PCM region signaloutputted from the PCM region signal generator 52. Also with thealternative construction, similar effects to those of the magneticrecording and reproducing apparatus of FIG. 15 described above can beachieved.

Further, while a PCM audio signal is inserted into a vertical blankingperiod of an FM modulated video signal in accordance with a suitablechange over operation of the switches 13 and 14 in the modified magneticrecording and reproducing apparatus of FIG. 19, it may be inserted insome other way into an FM modulated video signal. For example, a PCMaudio signal may be inserted in several separate parts into a horizontalblanking period of an FM modulated video signal. Further, also in thecase wherein a PCM audio signal for one field is inserted in severalparts into a segment blanking period and a vertical blanking period ofan FM modulated video signal and recorded onto and then reproduced froma magnetic tape in a video tape recorder of the type wherein a videosignal for one field is separated into a plurality of segments andrecorded onto and reproduced from a magnetic tape, if such constructionis employed that a region of a PCM audio signal in a reproduction signalis identified to generate a controlling signal representative of suchPCM audio signal region and a switch circuit selects, in accordance withsuch controlling signal, a reproduction FM demodulated signal in a videosignal region but selects an output of a delay element in a PCM audiosignal region, similar effects can be exhibited with such a recordingformat wherein a PCM audio signal is recorded in a segment blankingperiod.

Further, while a PCM audio signal mixed in a reproduction FM videosignal is FM demodulated as it is as a reproduction signal uponreproduction in the modified magnetic recording and reproducingapparatus of FIG. 19, even with a possible alternate constructionwherein an FM video signal and a PCM audio signal in a reproductionsignal are separated from each other before such FM video signal is FMdemodulated, a reproduction video signal after FM demodulation willinclude such noises in a PCM audio signal region as seen in FIG. 54.Accordingly, if such construction is employed similarly as in themodified magnetic recording and reproducing apparatus of FIG. 11 thatthe switch circuit is changed over in accordance with a PCM regionsignal outputted from the PCM region signal generator.

Referring now to FIG. 21, there is shown a modification to the modifiedmagnetic recording and reproducing apparatus shown in FIG. 19. Thepresent magnetic recording and reproducing apparatus is modified suchthat a delay element 55 is provided in place of the delay element 54 andconnected to the de-emphasis circuit 22 such that one of an output ofthe de-emphasis circuit 22 and an output of the delay element 55 may beselected by the switch circuit 53 in accordance with a PCM region signalfrom the PCM region signal generator 52 in the PCM decoder 51. Here, thedelay element 55 has a delay time τ which is longer than a period of aPCM audio signal region as seen from waveforms (a) and (b) of FIG. 22.Thus, the switch circuit 53 selects, in accordance with a PCM regionsignal from the PCM region signal generator 52, one of a reproductionvideo signal (waveform (a) in FIG. 22) outputted from the de-emphasiscircuit 22 and an output (waveform (b) in FIG. 22) of the delay element55. Thus, the switch circuit 53 outputs such a waveform (c) as shown inFIG. 22 wherein a signal in a PCM audio signal region of a reproductionvideo signal is replaced by data preceding by an interval of time equalto a period of a PCM audio signal region of the preceding field.

Referring now to FIG. 23, there is shown a magnetic recording andreproducing apparatus according to a fourth preferred embodiment of thepresent invention. The magnetic recording and reproducing apparatusshown includes a recording system including an analog to digital (A/D)converter 1 for converting an input video signal from an analog signalinto a digital signal, a first synchronizing separator circuit 2 forseparating a synchronizing signal from an input video signal, arecording signal processing circuit 3 for performing such recordingsignal processing as to insert blanking data, which make, uponreproduction, a reference signal for such processing as time basecorrection, into a video signal in accordance with a synchronizingsignal from the first synchronizing separator 2, a vertical blankingdata generator 57 operable upon recording and reproduction forgenerating, in accordance with a synchronizing separation signal fromthe first synchronizing separator circuit 2, blanking data for avertical blanking period of a video signal, a gate pulse for enablingvertical blanking data to be inserted into video signal data from therecording signal processing circuit 3 and a timing pulse for inserting aPCM audio signal into an FM video signal, a selector 58 operable uponrecording and reproduction for inserting vertical blanking data from thevertical blanking data generator 57 into video signal data from therecording signal processing circuit 3, and a digital to analog (D/A)converter 59 operable upon recording and reproduction for converting anoutput signal of the selector 59 from a digital signal into an analogsignal. The recording system of the magnetic recording and reproducingapparatus further includes an FM modulator 11, a PCM encoder 12, a pairof switches 13 and 14, an adder 15, a recording amplifier 16 and arecording video head 17, which are similar to the FM modulator 11, PCMencoder 12, switches 13 and 14, adder 15, recording amplifier 16 andrecording video head 17, respectively, of the recording system of themagnetic recording and reproducing apparatus shown in FIG. 11.

The magnetic recording and reproducing apparatus further includes areproducing system which includes a reproducing video head 18, areproduction amplifier 19, a reproduction equalizer 20, an FMdemodulator 21, a clamp circuit 24, an analog to digital (A/D) converter25, a second synchronizing separator circuit 26, a reproduction signalprocessing circuit 27 and a digital to analog (D/A) converter 28 whichare all similar to the respective corresponding ones of the reproducingsystem of the magnetic recording and reproducing apparatus shown in FIG.11. The reproducing system of the magnetic recording and reproducingapparatus further includes a PCM decoder 61 for decoding an outputsignal of the reproduction amplifier 19, that is, for detecting a PCMaudio signal for one field inserted in a vertical blanking period of areproduction signal and processing the detected PCM audio signal byerror correction, shuffling and so forth to restore an original audiosignal. The PCM decoder 61 includes therein a PCM region signalgenerator 62 which discriminates a region of a PCM modulated audiosignal in a reproduction signal and generates a PCM region signalrepresentative of a PCM audio signal region. The reproducing system ofthe magnetic recording and reproducing apparatus further includes aswitch circuit 60 for change over in accordance with a PCM region signalreceived from the PCM region signal generator 62 in the PCM decoder 61.

In operation, an input video signal upon recording is first convertedfrom an analog signal into a digital signal by the A/D converter 1 andthen outputted to the recording signal processing circuit 3. Meanwhile,the input video signal is also inputted to the first synchronizingseparator circuit 2, at which a synchronizing signal is separated fromthe input video signal. At the recording signal processing circuit 3,such recording signal processing as to insert blanking data, which make,upon reproduction, a reference signal for such processing as time basecorrection, into a video signal is performed in accordance with asynchronizing separation output from the first synchronizing separator2, and the thus processed signal is transmitted from the recordingsignal processing circuit 3 to the selector 58. Meanwhile, at thevertical blanking data generator 57, vertical blanking data for a videosignal and a gate pulse for enabling such vertical blanking data intovideo signal data received from the recording signal processing circuit3 are generated, upon recording, with reference to the synchronizingseparation output of the first synchronizing separator circuit 2 and areoutputted to the selector 58. The vertical blanking data generator 57further operates to generate a timing pulse for inserting a PCM audiosignal into a vertical blanking period of an FM video signal and outputit to the switches 13 and 14.

The vertical blanking data outputted from the vertical blanking datagenerator 57 are inserted by the selector 58 into the video signal datareceived from the recording signal processing circuit 3 in accordancewith a gate pulse from the vertical blanking data generator 57. Then,the video signal data in which the vertical blanking data are insertedare transmitted to the D/A converter 59, at which they are convertedfrom a digital signal into an analog signal. A waveform of a recordingvideo signal outputted from the D/A converter 59 is shown in FIG. 56.The recording video signal is subsequently supplied to the FM modulator11 while an input audio signal is supplied to the PCM encoder 12,whereafter the video signal and audio signal are processed by the FMmodulator 11 and PCM encoder 12, switches 13 and 14, adder 15 andrecording amplifier 16 and recorded onto a magnetic tape 200 by means ofthe recording video head 17 in a similar manner as in the magneticrecording and reproducing apparatus of FIG. 11 described hereinabove.

It is to be noted that the vertical blanking data generator 57 of therecording system operates also upon reproduction and normally generatesvertical blanking data, which are to make such a vertical blankingsignal as shown in FIG. 26 after digital to analog conversion thereof,in synchronism with a rotary drum not shown on which the recording andreproducing video heads 17 and 18 are mounted. Such vertical blankingdata are transmitted to the selector 58, and upon reproduction, theselector 58 always selects the output of the vertical blanking datagenerator 57. An output of the selector 58 is converted from a digitalsignal into an analog signal by the D/A converter 27. Then, the verticalblanking signal (FIG. 26) outputted from the D/A converter 27 afterconversion into an analog signal is sent to the switch circuit 60.

Meanwhile, upon reproduction, the components 18, 19, 20, 21, 24, 25, 26,27, 28, 61 and 62 of the reproducing system of the magnetic recordingand reproducing apparatus operate in a similar manner to the components18, 19, 20, 21, 24, 25, 26, 27, 28, 34 and 35, respectively, of thereproducing system of the magnetic recording and reproducing apparatusof FIG. 11 described hereinabove.

Accordingly, similarly as described hereinabove, if, upon reproduction,a reproduction FM video signal and a PCM audio signal mixed with suchreproduction FM video signal outputted from the reproduction equalizer20 are FM demodulated as they are by the FM demodulator 21, then thereproduction video signal after such FM demodulation will present suchan output signal waveform as shown in FIG. 54 as if it includes noise ina PCM audio signal region.

Thus, a reproduction video signal outputted from the FM demodulator 21is inputted to the switch circuit 60 which is changed over in accordancewith a PCM region signal representative of a PCM audio signal region sothat a signal in a PCM audio signal region of a reproduction videosignal is changed over to such a vertical blanking signal as shown inFIG. 26 which is generated by the vertical scanning data generator 57 ofthe recording system, thereby to obtain such a signal as shown in FIG.27.

Here, a PCM region signal generated by the PCM region signal generator62 in the PCM decoder 61 is transmitted to the switch circuit 60 so thata vertical blanking signal outputted from the D/A converter 59 of therecording system and a reproduction video signal from the FM demodulator21 are selectively outputted from the switch circuit 60 in response tosuch PCM region signal.

In particular, if, for example, such a pulse which presents a low levelin a video signal region but presents a high level in a PCM audio signalregion as shown by a waveform (a) in FIG. 28 is generated by the PCMregion signal generator 62 in the PCM decoder 61 and transmitted to theswitch circuit 60, the switch circuit 60 selects, in a period of a videosignal region in which the pulse present a low level, a reproductionvideo signal (waveform (b) shown in FIG. 28) transmitted thereto fromthe FM demodulator 21, but selects, in a period of a PCM audio signalregion in which the pulse presents a high level, a vertical blankingsignal (waveform (c) shown in FIG. 28) generated by the verticalblanking data generator 57 of the recording system and received from theD/A converter 59. Consequently, a signal in a PCM audio signal region atthe output of the switch circuit 60 is changed over to a verticalblanking signal generated by the recording system as seen from awaveform (d) of FIG. 28.

Where such construction is employed, a signal in a PCM audio signalregion of an FM demodulated reproduction video signal can be replaced bya vertical blanking signal generated by the recording system, andconsequently, synchronization separation of a video signal can beperformed accurately and the clamp circuit at a next stage can operatenormally. Further, since a signal to which a synchronizing signal isadded is inserted also in a signal in a PCM audio signal region, asignal can be clamped even in a PCM audio signal region, andconsequently, sags can be reduced.

A reproduction video signal outputted from the switch circuit 60 isthereafter processed by the clamp circuit 24, A/D converter 25, secondsynchronizing separator circuit 26, reproduction signal processingcircuit 27 and D/A converter 28 in a similar manner as describedhereinabove in connection with the magnetic recording and reproducingapparatus of FIG. 11. Consequently, a good output reproduction videosignal can be obtained from the reproducing system.

It is to be noted that, while the vertical blanking data generator 57 ofthe recording system of the magnetic recording and reproducing apparatusshown in FIG. 23 generates and outputs, upon reproduction, such verticalblanking data as shown in FIG. 26, it need not generate such specificwaveform data but may generate data of some other signal waveform whichmakes a reference signal to a video signal such as, for example, a rampsignal waveform, a gray signal or a black level signal in order toachieve similar effects to those described above.

Further, while the PCM region signal generator 62 generates a pulsewhich presents a low level in a video signal region but presents a highlevel in a PCM audio signal region, it may otherwise generate a pulsehaving an inverted phase while the switch circuit 60 is constructed suchthat it may select, in a video signal region, a reproduction videosignal outputted from the FM demodulator 21 but select, in a PCM audiosignal region, a vertical blanking signal generated by the recordingsystem and received from the D/A converter 59 in accordance with a PCMregion signal outputted from the PCM region signal generator 62. Alsowith the alternate construction, similar effects to those describedabove can be achieved.

Further, while vertical blanking data are generated in the form of adigital data and selected by the selector 58 and then converted intoanalog data, they may otherwise be generated and selected in the form ofan analog signal, by which similar effects can be achieved.

Further, while a PCM audio signal is inserted into a vertical blankingperiod of an FM modulated video signal in accordance with a suitablechange over operation of the switches 13 and 14 in the magneticrecording and reproducing apparatus of FIG. 23, it may be inserted insome other way into an FM modulated video signal. For example, a PCMaudio signal may be inserted in several separate parts into a horizontalblanking period of an FM modulated video signal. Further, also in thecase wherein a PCM audio signal for one field is inserted in severalparts into a segment blanking period and a vertical blanking period ofan FM modulated video signal and recorded onto and then reproduced froma magnetic tape in a video tape recorder of the type wherein a videosignal for one field is separated into a plurality of segments (a casewherein a video signal is separated into two segments is illustrated inFIG. 58) and recorded onto and reproduced from a magnetic tape, if suchconstruction is employed that a region of a PCM audio signal in areproduction signal is identified by a PCM region signal generator and acontrol signal representative of such PCM audio signal region isgenerated so as to change over a switch circuit in accordance therewith,similar effects can be exhibited with such a recording format wherein aPCM audio signal is recorded in a segment blanking period as shown inFIG. 58.

Furthermore, while a signal is replaced by blanking data generated bythe recording system in a PCM audio signal region of a reproductionvideo signal, similar effects can be exhibited also where a signalgenerated by a signal generator which generates a signal to make areference signal to a video signal is selected by a switch circuit inaccordance with a PCM region signal.

Referring now to FIG. 24, there is shown a modification to the magneticrecording and reproducing apparatus of FIG. 23 described above. Thepresent magnetic recording and reproducing apparatus is modified suchthat a PCM signal separator circuit 63 is interposed between thereproduction equalizer 20 and the FM demodulator 21 so that an FM videosignal and a PCM audio signal of a reproduction signal outputted fromthe reproduction equalizer 20 are separated from each other inaccordance with a PCM region signal outputted from the PCM region signalgenerator 62 in the PCM decoder 61 and the thus separated FM videosignal is transmitted to the FM demodulator 21.

Also in this instance, a reproduction video signal after FM demodulationwill present such an output signal waveform as seen from a waveform (c)of FIG. 57 and the waveform of FIG. 54 as if it includes noise in a PCMaudio signal region. Thus, similarly as in the magnetic recording andreproducing apparatus shown in FIG. 23, the switch circuit 60 selects,in a video signal region, a reproduction video signal outputted from theFM demodulator 21 but selects, in a PCM audio signal region, a verticalblanking signal generated by the recording system and received from theD/A converter 59 in accordance with a PCM region signal outputted fromthe PCM region signal generator 62 in the PCM decoder 61, therebyachieving similar effects to those described above.

Referring now to FIG. 25, there is shown another modification to themagnetic recording and reproducing apparatus of FIG. 23. The presentmagnetic recording and reproducing apparatus is modified such that therecording system thereof includes a vertical blanking data generator 68,a selector 69, a digital to analog (D/A) converter 70 and an FMmodulator 71 in place of the vertical blanking data generator 57,selector 58, D/A converter 59 and FM modulator 11 and the reproducingsystem thereof includes a PCM decoder 65 including a PCM region signalgenerator 66 therein and a switch circuit 67 in place of the PCM decoder61 including the PCM region signal generator 62 therein and the switchcircuit 60. The switch circuit 67 here in the present reproducing systemis interposed not between the FM demodulator 21 and the clamp circuit 24but between the reproduction equalizer 20 and the FM demodulator 21.

The vertical blanking data generator 68 operates upon recording andreproduction and generates vertical blanking data of a video signal inaccordance with a synchronizing separation signal from the firstsynchronizing separator circuit 2. The selector 69 also operates uponrecording and reproduction and inserts vertical blanking data from thevertical blanking data generator 68 into video signal data from therecording signal processing circuit 3. Further, the D/A converter 70also operates upon recording and reproduction and converts an outputsignal of the selector 69 from a digital signal into an analog signal.The PCM decoder 61 decodes an output signal of the reproductionamplifier 19, that is, detects a PCM audio signal for one field insertedin a vertical blanking period of a reproduction signal and processes thedetected PCM audio signal by error correction, shuffling and so forth torestore an original audio signal. The PCM region signal generator 62 inthe PCM decoder 61 discriminates a region of a PCM modulated audiosignal in a reproduction signal and generates a PCM region signalrepresentative of a PCM audio signal region.

In operation, an input video signal upon recording is first convertedfrom an analog signal into a digital signal by the A/D converter 1 andthen outputted to the recording signal processing circuit 3. Meanwhile,the input video signal is also inputted to the first synchronizingseparator circuit 2, at which a synchronizing signal is separated fromthe input video signal. At the recording signal processing circuit 3,such recording signal processing as to insert blanking data,.which make,upon reproduction, a reference signal for such processing as time basecorrection, into a video signal is performed in accordance with asynchronizing separation output from the first synchronizing separatorcircuit 2, and the thus processed signal is transmitted from therecording signal processing circuit 3 to the selector 69. Meanwhile, atthe vertical blanking data generator 68, vertical blanking data for avideo signal and a gate pulse for enabling such vertical blanking datato be inserted into video signal data received from the recording signalprocessing circuit 3 are generated, upon recording, with reference tothe synchronizing separation output of the first synchronizing separatorcircuit 2 and outputted to the selector 69. The vertical blanking datagenerator 68 further operates to generate a timing pulse for inserting aPCM audio signal into an FM video signal of an FM video signal andoutput it to the switches 13 and 14.

The vertical blanking data outputted from the vertical blanking datagenerator 68 are inserted by the selector 69 into the video signal datareceived from the recording signal processing circuit 3 in accordancewith a gate pulse from the vertical blanking data generator 68. Then,the video signal data in which the vertical blanking data are insertedare transmitted to the D/A converter 70, at which they are convertedfrom a digital signal into an analog signal, whereafter they areinputted to and FM modulated by the FM modulator 71. A waveform of suchrecording video signal outputted from the D/A converter 70 is shown inFIG. 56.

Meanwhile, an input audio signal inputted to the recording system issupplied to the PCM encoder 12, at which processing of shuffling,addition of an error correction code and so forth is performed thereforand then time base compressing processing is performed for the thusprocessed audio signal in accordance with a timing pulse received fromthe vertical blanking data generator 68 in order to allow the audiosignal for one field period to be later inserted into a fixed portion Ofa vertical blanking period of the FM video signal. The PCM encoder 12outputs the thus PCM modulated audio signal therefrom. Then, theswitches 13 and 14 are changed over in accordance with a timing pulsefrom the vertical blanking data generator 68 so that a PCM audio signalfor one field outputted from the PCM encoder 12 and an FM modulatedvideo signal outputted from the FM modulator 71 are added to each othersuch that the PCM audio signal may be inserted into a vertical blankingperiod of the FM modulated video signal as seen in FIG. 54 to produce arecording signal. The recording signal including the PCM audio signaland FM modulated video signal and outputted from the adder 15 issupplied to the recording amplifier 16, at which the FM video signal andthe PCM audio signal thereof are amplified. The composite recordingsignal of the FM video signal and the PCM audio signal is then recordedonto a magnetic tape 200 by means of the recording video head 17.

It is to be noted that the vertical blanking data generator 68 of therecording system operates also upon reproduction and normally generatesvertical blanking data, which will make such a vertical blanking signalas shown in FIG. 26 after digital to analog conversion thereof, insynchronism with a rotary drum not shown on which the recording andreproducing video heads 17 and 18 are mounted. Such vertical blankingdata are transmitted to the selector 69, and upon reproduction, theselector 69 always selects the output of the vertical blanking datagenerator 68. An output of the selector 69 is converted from a digitalsignal into an analog signal by the D/A converter 70. Then, the verticalblanking signal (FIG. 26) outputted from the D/A converter 70 afterconversion into an analog signal is inputted to the FM modulator 71, atwhich it is FM modulated. Then, the thus FM modulated vertical blankingsignal outputted from the FM modulator 34 is transmitted to the switchcircuit 67.

On the other hands upon reproduction, a reproduction signal reproducedfrom the magnetic tape 200 by the reproducing video head 18 is amplifiedby the reproduction amplifier 19 and transmitted to the reproductionequalizer 20 and also to the PCM decoder 65. At the PCM decoder 65, aPCM audio signal for one field inserted in a vertical blanking period ofsuch reproduction signal is detected and then processed by errorcorrection, de-shuffling, error modification and so forth to restore anoriginal audio signal. In the meantime, the reproduction equalizer 20compensates for a frequency characteristic of the reproduction FM videosignal in the reproduction signal received from the reproductionamplifier 19.

Here, similarly as in the magnetic recording and reproducing apparatusof FIG. 23, a PCM audio signal is added, upon recording, to a verticalblanking period of an FM video signal in accordance with suitablechanging over of the switches 13 and 14, and accordingly, a PCM audiosignal mixed with a reproduction FM video signal is outputted as it isfrom the reproduction equalizer 20. Thus, if an output of thereproduction equalizer 20 is FM demodulated by the FM demodulator 21,then a reproduction video signal outputted from the FM demodulator 21will present such an output signal waveform as shown in FIG. 54 as if itincludes noises in a PCM audio signal region.

Thus, a reproduction video signal outputted from the reproductionequalizer 20 is inputted to the switch circuit 67 which is changed overin accordance with a PCM region signal representative of a PCM audiosignal region so that the reproduction signal may be partially changedover to an FM signal obtained by FM modulation of a vertical blankingsignal by the FM modulator 71 of the recording system and outputted tothe FM demodulator 21. FIG. 27 shows a waveform of a reproduction videosignal outputted from the FM demodulator 21. Here, a PCM region signalgenerated by the PCM region signal generator 66 in the PCM decoder 65 istransmitted to the switch circuit 67 so that an FM modulated verticalblanking signal outputted from the FM modulator 71 of the recordingsystem and a reproduction signal outputted from the reproductionequalizer are selectively outputted from the switch circuit 67 inresponse to such PCM region signal.

In particular, if, for example, such a pulse which presents a low levelin a video signal region but presents a high level in a PCM audio signalregion generated by the PCM region signal generator 66 in the PCMdecoder 65 and transmitted to the switch circuit 67, the switch circuit67 selects, in a period of a video signal region in which the pulsepresents a low level, a reproduction video signal transmitted theretofrom the reproduction equalizer 20, but selects, in a period of a PCMaudio signal region in which the pulse presents a high level, an FMsignal obtained by FM modulation of a vertical blanking signal generatedby the vertical blanking data generator 68 of the recording system.Accordingly, a signal in a PCM audio signal region at the output of theswitch circuit 67 is changed over to a signal obtained by FM modulationof a vertical blanking signal generated by the recording system.

An output of the switch circuit 67 is inputted to the FM demodulator 21,at which it is FM demodulated into such a reproduction video signal asshown in FIG. 27. Thus, since a signal in a PCM audio signal region ofan FM demodulated reproduction video signal is replaced by a verticalblanking signal generated by the recording system, synchronizationseparation of a video signal can be performed accurately and the clampcircuit 24 at a next stage can operate normally. Further, since a signalto which a synchronizing signal is added is inserted also in a signal ina PCM audio signal region, a signal can be clamped even in a PCM audiosignal region, and consequently, sags can be reduced.

A reproduction video signal outputted from the FM demodulator 21 isthereafter processed by the clamp circuit 24, A/D converter 25, secondsynchronizing separator circuit 26, reproduction signal processingcircuit 27 and D/A converter 28 in a similar manner as describedhereinabove in connection with the magnetic recording and reproducingapparatus of FIG. 23 so that a good output reproduction video signal canbe produced.

It is to be noted that, while the vertical blanking data generator 68 ofthe recording system of the magnetic recording and reproducing apparatusshown in FIG. 25 generates and outputs, upon reproduction, such verticalblanking data as shown in FIG. 26, it need not generate such specificwaveform data but may generate data of some other signal waveform whichmakes a reference signal to a video signal such as, for example, a rampsignal waveform, a gray signal or a black level signal in order toachieve similar effects to those described above.

Further, while the PCM region signal generator 62 generates a pulsewhich presents a low level in a video signal region but presents a highlevel in a PCM audio signal region, it may otherwise generate a pulsehaving an inverted phase while the switch circuit 67 is constructed suchthat it may select, in a video signal region, a reproduction videosignal outputted from the 123 reproduction equalizer 20, but select, ina PCM audio signal region, a signal obtained by FM demodulation of avertical blanking signal generated by the recording system and receivedfrom the FM modulator 71 in accordance with a PCM region signaloutputted from the PCM region signal generator 66. Also with suchalternate construction, similar effects to those described above can beachieved.

Further, while vertical blanking data are generated in the form of adigital data and selected by the selector 69 and then converted intoanalog data and FM modulated, they may otherwise be generated, selectedand FM modulated in the form of an analog signal, by which similareffects can be achieved.

Further, while the magnetic recording and reproducing apparatus of FIG.25 is constructed such that a PCM audio signal mixed with a reproductionFM video signal is inputted as it is, upon reproduction, to the switchcircuit 67, similar effects to those described above can be achievedeven where it is modified such that the PCM signal separator circuit 63at the preceding stage to the FM demodulator 21 of the magneticrecording and reproducing apparatus of FIG. 24 is used to separate an FMvideo signal and a PCM audio signal of a reproduction signal from thereproduction equalizer 20 from each other as seen from the waveform (b)of FIG. 57 and then the thus separated FM video signal is inputted tothe switch circuit 67 so that, in accordance with a PCM region signaloutputted from the PCM region signal generator 66, the reproduction FMvideo signal after separation from the PCM video signal may be selectedin a video signal region, but a signal obtained by FM modulation by theFM modulator 71 of a blanking signal generated by the recording systemmay be selected in a PCM audio signal region.

Further, while a PCM audio signal is inserted into a vertical blankingperiod of an FM modulated video signal in accordance with a suitablechange over operation of the switches 13 and 14 in the magneticrecording and reproducing apparatus of FIG. 25, it may be inserted insome other way into an FM modulated video signal. For example, a PCMaudio signal may be inserted in several separate parts into a horizontalblanking period of an FM modulated video signal. Further, also in thecase wherein a PCM audio signal for one field is inserted in severalparts into a segment blanking period and a vertical blanking period ofan FM modulated video signal and recorded onto and then reproduced froma magnetic tape in a video tape recorder of the type wherein a videosignal for one field is separated into a plurality of segments (a casewherein a video signal is separated into two segments is illustrated inFIG. 58) and recorded onto and reproduced from a magnetic tape, if suchconstruction is employed that a region of a PCM audio signal in areproduction signal is identified by a PCM region signal generator and acontrol signal representative of such PCM audio signal region isgenerated so as to change over a switch circuit in accordance therewith,similar effects can be exhibited with such a recording format wherein aPCM audio signal is recorded in a segment blanking period as shown inFIG. 69.

Furthermore, while a signal is replaced by blanking data generated bythe recording system in a PCM audio signal region of a reproductionvideo signal, similar effects can be exhibited also where a signalgenerated by a signal generator which generates an FM modulated signalof a signal to make a reference signal to a video signal is selected bya switch circuit in accordance with a PCM region signal.

Referring now to FIG. 29, there is shown a magnetic recording andreproducing apparatus according to a fifth preferred embodiment of thepresent invention. The magnetic recording and reproducing apparatusincludes a recording system which is common in construction to therecording system of the magnetic recording and reproducing apparatusdescribed hereinabove with reference to FIG. 1. The magnetic recordingand reproducing apparatus further includes a reproducing system whichincludes a reproducing video head 18, a reproduction amplifier 19, areproduction equalizer 20, an FM demodulator 21, a de-emphasis circuit22 and a PCM decoder 34 including a PCM region signal generator 35therein, similarly to the reproducing system of the magnetic recordingand reproducing apparatus of FIG. 1. The reproducing system of thepresent magnetic recording and reproducing apparatus further includes ananalog to digital (A/D) converter 72 connected to the reproductionamplifier 19, a memory 73 connected to the A/D converter 72 for storinga reproduction FM signal therein, and a digital to analog converter 74interposed between the memory 73 and the reproduction equalizer 20.

In operation, the recording system of the magnetic recording andreproducing apparatus operates, upon recording, in a similar manner asin the recording system of the magnetic recording and reproducingapparatus of FIG. 1.

On the other hand, upon reproduction, a reproduction signal read outfrom the magnetic tape 200 by means of the reproducing magnetic head 18is first amplified by the reproduction amplifier 19 and then transmittedto the A/D converter 72 and the PCM decoder 34. The PCM decoder 34 thusdecodes and outputs a PCM audio signal in the reproduction signal. Atthe same time, the PCM region signal generator 35 in the PCM decoder 34generates a PCM region signal representative of a PCM audio signal insuch a manner as described above. Thus, the PCM region signal generator35 generates for example, such a PCM region signal which presents a lowlevel in a PCM audio region but presents a high level in a video signalregion as seen from a waveform (b) of FIG. 30.

Meanwhile, the reproduction FM signal having such a waveform as shown bya waveform (a) in FIG. 30 is converted into a digital signal by the A/Dconverter 72. The digital signal outputted from the A/D converter 72 isthen stored into the memory 73 in response to a write clock signalsynchronized with a sampling clock supplied to the A/D converter 72. Thewrite address of the memory 73 is set such that it is cleared inresponse to such write clock signal and a PCM region signal from the PCMregion signal generator 35 at a point of time when the PCM region signalchanges from a low level to a high level, and after then, it isincremented successively in response to the write clock signal as seenfrom a waveform (e) of FIG. 30. Thus, the reproduction FM signal for onefield is successively written into the memory 73 in accordance with suchwrite address. It is to be noted that n+1 in FIG. 30 represents a numberof samples of a reproduction FM signal for one field while 1 denotes anumber of samples of a PCM audio signal.

When the thus stored data are to be read out from the memory 73, a readclock signal is produced in such a manner as given by the followingexpression:

    (read clocks)=(write clocks)×(m/(m+1))

so that the PCM audio signal data of the stored reproduction FM signaldata may not be read out. Thus, the read address of the memory 73 is setsuch that it is cleared at a point of time when the PCM region signalchanges from a low level to a high level, and it is successivelyincremented in response to the read clock signal in response to the thusproduced read clock signal and the PCM region signal described above.Thus, the reproduction signal data except the PCM audio signal data areread out from the memory 73 in accordance with such read address,thereby obtaining such an output signal as seen from a waveform (c) inFIG. 30.

A signal free from a PCM audio signal is produced in this manner from areproduction FM signal. The signal thus produced is re-converted into ananalog signal by the. D/A converter 74 and then transmitted to thereproduction equalizer 20. At the reproduction equalizer 20, a frequencycharacteristic of a reproduction FM video signal of the reproductionsignal transmitted thereto is compensated for, and an output signal ofthe reproduction equalizer 20 is transmitted to the FM demodulator 21,at which it is FM demodulated. The FM demodulated reproduction videosignal is then transmitted to the de-emphasis circuit 22, at which highfrequency components emphasized by the pre-emphasis circuit 10 in therecording system are de-emphasized so that a reproduction video signalfrom which high frequency noises have been removed and also a PCM audiosignal has been removed is obtained.

Thus, with the magnetic recording and reproducing apparatus describedjust above, a PCM audio signal can be removed from a reproduction FMsignal, and synchronizing separation is performed from a video signalafter FM demodulation of such reproduction FM signal, synchronizingseparation can be performed accurately without being influenced by a PCMaudio signal which makes a noise in the course of such FM demodulation,and consequently, a stabilized reproduction video signal can beobtained. It is to be noted that, if a video signal is time baseelongated and FM demodulated in the course of removal of a PCM audiosignal, the level of the reproduced video signal will relatively dropcomparing with a video signal level upon recording. However, such levelof the video signal can be corrected by a time base correcting circuit(not shown) which may be connected to the de-emphasis circuit 22.

Referring now to FIG. 31, there is shown a modification to thereproducing system of the magnetic recording and reproducing apparatusof FIG. 29. The reproducing system is modified such that thereproduction equalizer 20 is interposed between the reproductionamplifier 19 and the A/D converter 72 and a de-emphasis circuit 75 whichhas a same characteristic as the de-emphasis circuit 22 but processesnot an analog signal but a digital signal is provided in place of thede-emphasis circuit 22 while a digital FM demodulator 77 is provided inplace of the D/A converter 74 and FM modulator 21 and interposed betweenthe memory 73 and the de-emphasis circuit 75. The digital FM demodulator77 receives a reproduction FM signal in the form of a digital signalfrom the memory 73 and FM demodulates the thus received reproduction FMsignal. An output reproduction signal from the FM demodulator 77 isinputted to the de-emphasis circuit 75, at which it is de-emphasizeddigitally. The de-emphasis circuit 75 thus outputs a reproduction signalin the form of a digital signal.

In operation, upon reproduction, a reproduction signal read out from themagnetic tape 200 by means of the reproducing magnetic head 18 is firstamplified by the reproduction amplifier 19 and then transmitted to thereproduction equalizer 20 and the PCM decoder 34. The PCM decoder 34thus decodes and outputs a PCM audio signal in the reproduction signal.Simultaneously, the PCM region signal generator 35 in the PCM decoder 34generates a PCM region signal representative of a PCM audio signal in asimilar manner as in the magnetic recording and reproducing apparatus ofFIG. 29.

Meanwhile, the reproduction equalizer 20 to which the reproduction FMsignal having such a waveform as shown by the waveform (a) in FIG. 30 isinputted compensates for a frequency characteristic of the inputtedreproduction FM video signal, and an output of the reproductionequalizer 20 is inputted to the A/D converter 72, at which it isconverted into a digital FM signal. Then, the reproduction digital FMsignal from the A/D converter 72 is successively stored into the memory73 in accordance with a write address which is produced so as tosuccessively increase in response to a write clock signal after thememory 73 was cleared at a point of time when the PCM region signal fromthe PCM region signal generator 35 changed from a low level to a highlevel.

When the thus stored data are to be read out from the memory 73, a readclock signal is set in such a manner as described hereinabove so thatthe PCM audio signal data of the stored reproduction FM signal data maynot be read out. Thus, the read address of the memory 73 is set suchthat it is cleared at a point of time when the PCM region signal changesfrom a low level to a high level, whereafter it is successivelyincremented in response to the read clock signal described above. Thus,the reproduction signal data except the PCM audio signal data are readout from the memory 73 in accordance with such read address, therebyobtaining such an output signal as seen from a waveform (c) in FIG. 30.

The digital FM signal from which such PCM audio signal has been removedis FM demodulated by the digital FM demodulator 77, and then highfrequency components which were emphasized by the pre-emphasis circuit10 in the recording system are de-emphasized by the de-emphasis circuit75 so that a reproduction video signal from which high frequency noiseshave been removed and also a PCM audio signal has been removed isobtained.

Thus, with the magnetic recording and reproducing apparatus describedjust above, similarly as in the magnetic recording and reproducingapparatus of FIG. 29, since an FM signal obtained by removal of a PCMaudio signal from a reproduction FM signal is FM demodulated andsynchronizing separation is performed using the thus FM demodulatedvideo signal, synchronizing separation can be performed accurately, andconsequently, a stabilized reproduction video signal can be obtained. Itis to be noted that, if a video signal is time base elongated and FMdemodulated in the course of removal of a PCM audio signal, the level ofthe reproduced video signal will relatively drop comparing with a videosignal level upon recording. However, such level of the video signal canbe corrected by a time base correcting circuit (not shown) which may beconnected to the de-emphasis circuit.

While the magnetic recording and reproducing apparatus of FIG. 29 and 31are constructed such that a PCM audio signal is inserted into a verticalblanking period of a video signal upon recording, even when a videosignal four one field or for one frame is divided into a plurality oftracks and a PCM audio signal is added to a first end or a last end ofeach of such tracks upon recording, synchronizing separation can beperformed accurately and a stabilized reproduction video signal can beobtained if similar means to that of the magnetic recording andreproducing apparatus of FIG. 29 is employed.

For example, a video signal for one field can be recorded divisionallyonto three tracks by the magnetic recording and reproducing apparatusshown in FIG. 29. In particular, upon recording, a video signal for onefield is divided into three segments while a vertical blanking period isdivided into three portions such that a segment blanking period may beprovided between adjacent ones of the segments as seen from a waveform(a) in FIG. 32, and then the video signal is FM modulated. Then, a PCMaudio signal and the FM video signal are added to each other in such amanner as seen from a waveform (b) of FIG. 32 by the adder 15 inresponse to a suitable change over operation of the switches 13 and 14.

Upon reproduction, a reproduction signal read out from the magnetic tape200 by means of the reproducing magnetic head 18 is first amplified bythe reproduction amplifier 19 and then transmitted to the A/D converter72 and the PCM decoder 34. The PCM decoder 34 thus decodes a PCM audiosignal in the reproduction signal and outputs a reproduction audiosignal. Simultaneously, the PCM region signal generator 35 in the PCMdecoder 34 generates a PCM region signal representative of a PCM audiosignal in a similar manner as in the magnetic recording and reproducingapparatus of FIG. 29 (refer to a waveform (b) in FIG. 33).

Meanwhile, the reproduction FM signal having such a waveform as shown bya waveform (a) in FIG. 33 is converted into a digital signal by the A/Dconverter 72. The digital signal outputted from the A/D converter 72 isthen stored into the memory 73 in response to a write clock signalsynchronized with a sampling clock supplied to the A/D converter 72. Thewrite address of the memory 73 is set such that it is cleared inresponse to such write clock signal and a PCM region signal from the PCMregion signal generator 35 at a point of time when the PCM write addresssignal changes from a low level to a high level, and after then, it isincremented successively in response to the write clock signal as seenfrom a waveform (d) of FIG. 33. Thus, the reproduction FM signal for onesegment is written into the memory 73 in accordance with such writeaddress. It is to be noted that ms+1s is in FIG. 33 represents a numberof samples of a reproduction FM signal for one segment while is denotesa number of samples of a PCM audio signal.

When the thus stored data are to be read out from the memory 73, a readclock signal is produced in such a manner as given by the followingexpression:

    (read clocks)=(write clocks)×(ms/(ms+1s))

so that the PCM audio signal data of the stored reproduction FM signaldata may not be read out. Thus, the read address of the memory 73 is setsuch that it is cleared at a point of time when the PCM region signalchanges from a low level to a high level, whereafter it is successivelyincremented in response to the read clock signal. Thus, the reproductionsignal data except the PCM audio signal data are read out from thememory 73 in accordance with such read address, thereby obtaining suchan output signal as seen from a waveform (c) in FIG. 33.

The output signal from the memory 73 free from a PCM audio signal isthen re-converted into an analog signal by the D/A converter 74 and thentransmitted to the reproduction equalizer 20, at which a frequencycharacteristic thereof is compensated for. Then, an output signal of thereproduction equalizer 20 is transmitted to the FM demodulator 21, atwhich it is FM demodulated. The FM demodulated reproduction video signalis then transmitted to the de-emphasis circuit 22, at which highfrequency components emphasized by the pre-emphasis circuit 10 in therecording system are de-emphasized. Consequently, a reproduction videosignal from which a PCM audio signal has been removed is FM demodulated.

While the case wherein a video signal for one field is recordeddivisionally onto three tracks, even in another case wherein a videosignal for one field or for one frame is recorded divisionally onto n(an integer equal to or greater than 2) tracks while a PCM audio signalis recorded additionally at a first end or a last end of each of suchtracks, similar effects can be achieved by using similar means.

The modified magnetic recording and reproducing apparatus shown in FIG.31 can be employed in order to realize such divisional recording of avideo signal. In particular, a PCM region signal representative of a PCMaudio signal region is generated from a reproduction FM signal by thePCM region signal generator 35 in the PCM decoder 34. A frequencycharacteristic of a reproduction FM signal from the reproductionamplifier 19 is compensated for by the reproduction equalizer 20, and anoutput of the reproduction equalizer 20 is converted into a digital FMsignal by the A/D converter 72. Then, the reproduction digital FM signalis successively stored into the memory 73 in accordance with a writeaddress which is produced so as to successively increase in response toa write clock signal after the memory 73 was cleared at a point of timewhen the PCM region signal from the PCM region signal generator 35changed from a low level to a high level.

When the thus stored data are to be read out from the memory 73, a readclock signal is set in such a manner as described hereinabove so thatthe PCM audio signal data of the stored reproduction FM signal data maynot be read out. Here, the read address of the memory 73 is set suchthat it is cleared at a point of time when the PCM region signal changesfrom a low level to a high level, whereafter it is successivelyincremented in response to the read clock signal. Thus, the reproductiondigital FM signal data except the PCM audio signal data are read outfrom the memory 73 in accordance with such read address.

The digital FM signal from which such PCM audio signal has been removedis FM demodulated by the digital FM demodulator 77, and then highfrequency components therein which were emphasized by the pre-emphasiscircuit 10 in the recording system are de-emphasized by the de-emphasiscircuit 75 so that a reproduction video signal from which a PCM audiosignal has been removed is obtained.

While, in the foregoing description of the magnetic recording andreproducing apparatus shown in FIGS. 29 and 31, a reproduction FM signalwritten in the memory 73 is read out in a time base elongated conditionin accordance with a PCM region signal generated by the PCM regionsignal generator 35 so that a PCM audio signal may be removed from thereproduction FM signal, it may be read out in a different manner. Forexample, a reproduction FM signal is written into the memory 73 in asimilar manner as described hereinabove (refer to a waveform (e) of FIG.34), and when it is to be read out from the memory 73, a period of aread clock signal is set equal to that of a write clock signal. The readaddress is reset at a point of time when the PCM region signal changesfrom a low level to a high level, and is thereafter incrementedsuccessively in response to the read clock signal (refer to a waveform(f) in FIG. 34). Then, the reproduction FM signal stored in the memory73 is read out in accordance with such read address. Consequently, suchan output signal as seen from a waveform (c) of FIG. 34 wherein a formerportion of a video signal for one field follows a latter portion of thevideo signal of the same field, that is, a signal from which a PCM audiosignal has been removed, is obtained.

It is also possible to set the read address otherwise such that it isreset at a point of time when the PCM region signal changes from a lowlevel to a high level, whereafter it is successively incremented whilethe PCM region signal remains at a high level but is successivelydecremented after the PCM region signal changes from a high level to alow level (refer to a waveform (c) of FIG. 35). Then, if the storedreproduction FM signal is read out from the memory 73 in accordance withthe address, then a video signal from which a PCM audio signal has beenremoved is obtained.

Alternatively, the read address may be set such that it is reset at apoint of time when the PCM region signal changes from a low level to ahigh level, whereafter it is successively incremented while the PCMregion signal remains at a high level, but after the PCM region signalchanges from a high level to a low level, part of the addresses isrepeated while the PCM region signal remains at a high level. Then, ifthe stored reproduction FM signal is read out from the memory 73 inaccordance with the read address, a video signal from which a PCM audiosignal has been removed is obtained.

Or else, the read address may be set such that it is reset at a point oftime when the PCM region signal changes from a low level to a highlevel, whereafter it is successively incremented while the PCM regionsignal remains at a high level, but part of the addresses is repeatedwhile the PCM region signal remains at a low level. Also in thisinstance, if the stored reproduction FM signal is read out from thememory 73 in accordance with the read address, then a video signal fromwhich a PCM audio signal has been removed is obtained.

In any case, since a reproduction FM signal from which a PCM audiosignal has been removed is FM modulated to obtain a video signal andsynchronizing separation is performed for such video signal,synchronizing separation can be performed accurately, and consequently,a stabilized reproduction video signal can be obtained.

Referring now to FIG. 36, there is shown a modification to thereproducing system of the magnetic recording and reproducing apparatusof FIG. 29. The modified reproducing system includes a CCD (chargecoupled device) 78 for storing a reproduction FM signal therein, inplace of the A/D converter 72, memory 73 and D/A converter 74.

In operation, upon reproduction, a reproduction signal read out from themagnetic tape 200 by means of the reproducing magnetic head 18 is firstamplified by the reproduction amplifier 19 and transmitted to the CCD 78and the PCM decoder 34. The PCM decoder 34 thus decodes a PCM audiosignal in the reproduction signal and outputs a reproduction audiosignal. Simultaneously, the PCM region signal generator 35 in the PCMdecoder 34 generates a PCM region signal representative of a PCM audiosignal in a similar manner as described hereinabove (refer to a waveform(c) in FIG. 37).

Meanwhile, the reproduction FM signal for one field from which the PCMaudio signal has been removed is successively stored into the CCD 78 inresponse to a write clock signal beginning with a point of time when thePCM region signal changes from a low level to a high level, but in a PCMaudio signal region, such write clock signal is stopped to stop writinginto the CCD 78 (refer to a waveform (c) of FIG. 37).

When the thus stored data are to be read out from the CCD 78, a readclock signal is produced in such a manner as given by the followingexpression:

    (read clocks)=(write clocks)×(mc/(mc+1c))

where 1 c is a period of a PCM audio signal for one field and mc+1c is aperiod of one field, so that a reproduction FM signal for one fieldexcept a PCM audio signal may be time base elongated to make a signalfor one field period. Using such read clock, a signal except a PCM audiosignal is read out from the CCD 78 (refer to a waveform (d) of FIG. 37.

The output signal from the CCD 78 free from a PCM audio signal is thentransmitted to the reproduction equalizer 20, at which a frequencycharacteristic thereof is compensated for. Then, an output signal of thereproduction equalizer 20 is transmitted to the FM demodulator 21, atwhich it is FM demodulated. The FM demodulated reproduction video signalis transmitted to the de-emphasis circuit 22, at which high frequencycomponents emphasized by the pre-emphasis circuit 10 in the recordingsystem are de-emphasized. Consequently, synchronizing separation isperformed using a video signal obtained by demodulation of areproduction FM signal from which a PCM audio signal has been removed isperformed, and accordingly, synchronizing separation can be performedaccurately without being influenced by a PCM audio signal which makes anoise in the course of FM demodulation. Consequently, a stabilizedreproduction video signal can be obtained.

The reproducing system may be used also for such case wherein a videosignal for one field or for one frame is recorded divisionally onto aplurality of tracks and a PCM audio signal is recorded additionally at afirst end or a last end of each of the tracks. In this instance, areproduction signal for each segment is written into the CCD 78, andthen the stored reproduction is read out from the CCD 78 in a time baseelongated condition while a read clock signal is set so that a PCM audiosignal may be removed. Consequently, similar effects can be achieved.

Such control as described hereinabove with reference to FIG. 34 may beperformed with the recording system of FIG. 36. In this instance, areproduction FM signal is written into the CCD 78 in such a manner asdescribed above. Meanwhile, a period of a read clock signal which isused upon reading from the CCD 78 is set equal to that of a write clocksignal. After the PCM region signal changes from a high level to a lowlevel, the reproduction FM signal stored in the CCD 78 is successivelyread out beginning with the top data thereof, but after the PCM regionsignal changes from a low level to a high level, the stored reproductionFM signal is successively read out beginning with the top data thereofagain. Consequently, a signal from which a PCM audio signal has beenremoved is obtained.

Similar effects can be attained otherwise if the stored reproduction FMsignal is successively read out, after the PCM region signal changesfrom a high level to a low level, from the CCD 78 beginning with thefirst data thereof, and after the PCM region signal changes from a lowlevel to a high level, the stored reproduction FM signal is read outbeginning with particular data thereof again.

Further, also in case a video signal for one field or for one frame isdivided into a plurality of channels and then each of the channels isdivided into a plurality of tracks and a PCM audio signal is recordedadditionally at a first end or a last end of each of the tracks, similareffects can be attained if the memory 73 or the CCD 78 is operated in asimilar manner as described hereinabove.

It is to be noted that similar effects can be attained if onlydemodulation of a PCM audio signal is inhibited when a reproduction FMsignal is digitally demodulated.

Referring now to FIG. 38, there is shown a magnetic recording andreproducing apparatus according to a sixth preferred embodiment of thepresent invention. The magnetic recording and reproducing apparatusincludes a recording system which is similar in construction to therecording system of the magnetic recording and reproducing apparatusshown in FIG. 23 except that it includes a recording signal processingcircuit 7 and a digital to analog (D/A) converter 6 in place of therecording signal processing circuit 3, vertical blanking data generator57 and selector 58 and the D/A converter 59, respectively, of themagnetic recording and reproducing apparatus of FIG. 23 and additionallyincludes a pre-emphasis circuit 10 connected to the D/A converter 6. Therecording signal processing circuit 7 performs recording signalprocessing such as to insert blanking data into an input video signalwith reference to a synchronizing signal outputted from the firstsynchronizing separator circuit 2. The recording signal processingcircuit 7 further operates to generate a timing pulse for inserting aPCM audio signal into an FM video signal. Such timing signal istransmitted to the PCM encoder 12 and also to the switches 13 and 14 soas to close or open the switches 13 and 14 in accordance therewith. Aninput video signal processed by the recording signal processing circuit7 is inputted to the D/A converter 6, at which it is converted from adigital signal into an analog signal. An analog output video signal ofthe D/A converter 6 is inputted to the pre-emphasis circuit 10, at whichhigh frequency components thereof are emphasized, and then inputted tothe FM modulator 11. It is to be noted that the magnetic recording andreproducing apparatus includes a pair of rotary heads 29a and 29b whicheach acts as a recording head and a reproducing head upon recording andreproduction, respectively. It is also to be noted that, different fromthe recording system of the magnetic recording and reproducing apparatusof FIG. 23, the recording signal processing circuit 7 and D/A converter6 of the present recording system do not operate upon reproduction.

The recording system of the magnetic recording and reproducing apparatusof FIG. 38 is substantially similar to the recording system of theconventional magnetic recording and reproducing apparatus shown in FIG.59 and described hereinabove.

The magnetic recording and reproducing apparatus further includes areproducing system which is also similar in construction to thereproducing system of the magnetic recording and reproducing apparatusof FIG. 23 except that it includes a pair of reproduction amplifiers 19aand 19b and a PCM decoder 79 in place of the single reproductionamplifier 19 and the PCM decoder 23, respectively, and additionallyincludes a head change over circuit 30 interposed between thereproduction amplifiers 19a and 19b and the reproduction equalizer 20, alimiter 32 connected to the reproduction equalizer 20, a switch circuit82 interposed between the limiter 32 and the FM demodulator 21, a delaycircuit 81 interposed between the limiter 32 and the switch circuit 82,and a de-emphasis circuit 22 interposed between the FM demodulator 21and clamp circuit 24. The reproduction amplifiers 19a and 19b amplifyreproduction signals from the rotary heads 29a and 29b, respectively,and the thus amplified reproduction signals are selectively transmittedby way of the head changing over circuit 30 in response to a headchanging over signal. The PCM decoder 79 is similar in construction tothe PCM decoder 61 described hereinabove and includes a PCM regionsignal generator 80 which is also similar in construction to the PCMregion signal generator 62 in the PCM decoder 61. The limiter 32receives an output reproduction FM video signal of the reproductionequalizer 20 and removes amplitude variation components from thereceived reproduction FM video signal. The delay element 81 has a delayperiod τ and delays an output signal bf the limiter 32 by such delayperiod τ. The switch circuit 82 selects one of an output signal of thelimiter 32 and an output signal of the delay element 81 in accordancewith a PCM region signal received from the PCM region signal generator80 of the PCM decoder 79. The de-emphasis circuit 22 has a reversecharacteristic to that of the pre-emphasis circuit 10 of the recordingsystem.

The reproducing system of the magnetic recording and reproducingapparatus of FIG. 38 is thus similar in construction to the reproducingsystem of the conventional magnetic recording and reproducing apparatusof FIG. 59 except that it includes, in place of the PCM decoder 31, thePCM decoder 79 including the PCM region signal generator 80 therein andadditionally includes the delay element 81 and switch circuit 82.

In operation, an input video signal is first converted from an analogsignal into a digital signal by the A/D converter 1 and then outputtedto the recording signal processing circuit 7. At the recording signalprocessing circuit 7, such recording signal processing as to insertblanking data is performed in accordance with a synchronizing separationoutput of the first synchronizing separator 2. The recording signalprocessing circuit 7 also generates and outputs a timing pulse forinserting a PCM audio signal into an FM video signal. An outputrecording signal of the recording signal processing circuit 7 isconverted from a digital signal into an analog signal by the D/Aconverter 6 and then inputted to the pre-emphasis circuit 10, at whichhigh frequency components thereof are emphasized. The recording videosignal is subsequently supplied to the FM modulator 11 while an inputaudio signal is supplied to the PCM encoder 12, whereafter the videosignal and audio signal are processed by the FM modulator 11 and PCMencoder 12, switches 13 and 14, adder 15 and recording amplifier 16 in asimilar manner as in the magnetic recording and reproducing apparatus ofFIG. 23 described hereinabove and then recorded onto a magnetic tape 200by means of the rotary heads 29a and 29b. In this instance, a changeover operation of the switches 13 and 14 is performed in response to atiming pulse transmitted thereto from the recording signal processingcircuit 7. Also the PCM encoder 12 operates in response to such timingpulse from the recording signal processing circuit 7.

It is to be noted that, in this instance, the recording signal isrecorded into two regions or tracks a and b by the rotary heads 29a and29b, respectively, while the rotary drum vertical blanking datagenerator 44 (FIG. 60) makes one full rotation such that a recordingsignal for one field is recorded onto one track, and a PCM audio signalis recorded in a time division multiplexed condition in a verticalblanking period of an FM video signal and thus at each of hatchedportions of the tracks a and b, similarly as in the conventionalmagnetic recording and reproducing apparatus of FIG. 59.

The thus recorded FM video signal and PCM audio signal are reproducedfrom the magnetic tape 200 by means of the rotary heads 29a and 29b andthen amplified by the reproducing amplifiers 19a and 19b. Then, suchreproduction signals outputted from the reproduction amplifiers 19a and19b as seen from the waveforms (a) and (b) shown in FIG. 62 areselectively transmitted by the head change over circuit 30 in responseto a head changing over signal so that a reproduction signal of a rotaryhead (FIG. 60) which currently contacts with the magnetic head 200 maybe selected thereby to form such a single reproduction signal as shownby the waveform (c) of FIG. 62. The reproduction signal from the headchanging over circuit 30 is then transmitted to the reproductionequalizer 20 and also to the PCM decoder 79. At the PCM decoder 79, aPCM audio signal for one field inserted in a vertical blanking period ofthe received reproduction signal is detected and then such signalprocessing as error correction, de-shuffling, error modification and soforth is performed for the thus detected PCM audio signal to restore anoriginal audio signal. The thus restored audio signal is outputted as anoutput signal of the recording system from the PCM decoder 79.Meanwhile, at the reproduction equalizer 20, a frequency characteristicof a reproduction FM video signal of the inputted reproduction signal iscompensated for, and then an output signal of the reproduction equalizer20 is transmitted to the limiter 32, at which amplitude variationcomponents of the reproduction FM video signal are removed.

By the way, if a reproduction FM video signal and a PCM audio signalmultiplexed in a vertical blanking period of such reproduction FM videosignal are FM demodulated as they are by the FM demodulator 21, thereproduction FM demodulated video signal presents such an output signalwaveform (a) as shown in FIG. 39 as if it includes noises in its PCMaudio signal region, similarly as in the conventional magnetic recordingand reproducing apparatus of FIG. 59.

Thus, the reproduction signal outputted from the limiter 32 istransmitted to the switch circuit 82 and delay element 81 so that asignal in a PCM audio signal region may be replaced by a reproduction FMvideo signal of a preceding field as seen from a waveform (b) of FIG.39. Here, a PCM region signal generated in a similar manner as describedhereinabove by the PCM region signal generator 80 in the PCM decoder 79and representative of a PCM audio signal region is transmitted to theswitch circuit 82.

The switch circuit 82 is thus changed over in accordance with the thusreceived PCM region signal such that it selects, in a video signalregion, a reproduction signal (waveform (a) in FIG. 40) outputted fromthe limiter 32, but selects, in a PCM audio signal region, such anoutput of the delay element 81 having the delay time τ as shown by awaveform (b) in FIG. 40. Since the delay element 81 outputs areproduction FM signal obtained by delaying a signal of a precedingfield to the PCM audio signal region by the delay time τ, the signal inthe PCM audio signal region is such a reproduction FM signal delayed fora period of the delay time τ of the preceding field as indicated by aportion A1 or A2 of a waveform (c) in FIG. 40.

Accordingly, a reproduction FM signal outputted from the switch circuit82 and inputted to the FM demodulator 21 is such a signal wherein areproduction FM signal obtained by delaying, for a period of the time τ,a signal of a preceding field to a vertical blanking period in which aPCM audio signal is inserted is inserted into a PCM audio signal regionas shown by the waveform (c) of FIG. 40. Consequently, if an output ofthe switch circuit 82 is demodulated by the FM demodulator 21 and highfrequency components thereof emphasized by the pre-emphasis circuit 10in the recording system are de-emphasized by the de-emphasis circuit 22,such a reproduction video signal wherein high frequency noises arereduced as shown by the waveform (b) of FIG. 39 is obtained. Thus, sincea signal in a PCM audio signal region is replaced by a reproductionvideo signal of a preceding field, synchronizing separation of areproduction video signal can be performed accurately, and consequently,the clamp circuit 24 operates normally. Further, a synchronizing signalis added also to a signal in a PCM audio signal region, andconsequently, a signal can be clamped also in a PCM audio signal regionand sags can be reduced.

A reproduction video signal outputted from the de-emphasis circuit 22 isinputted to the clamp circuit 24, at which an end portion of asynchronizing signal thereof is clamped at a predetermined dc voltagelevel. An output reproduction video signal of the clamp circuit 24 isconverted from an analog signal into a digital signal by the A/Dconverter 25 and transmitted to the reproduction signal processingcircuit 27. Meanwhile, the second synchronizing separator circuit 26separates a synchronizing signal from the reproduction video signal fromthe clamp circuit 24. The reproduction signal processing circuit 27performs such reproduction signal processing of the reproduction videosignal from the A/D converter 25 as time base correction or dropoutcompensation in accordance with a synchronizing separation output of thesecond synchronizing separator circuit 26, and a reproduction videosignal outputted from the reproduction signal processing circuit 27 isthen converted from a digital signal into an analog signal by the D/Aconverter 28 to produce an analog reproduction video signal. A goodreproduction video signal is thus obtained and outputted as an outputsignal of the reproducing system.

It is to be noted that, while the delay time of the delay element 81 ofthe magnetic recording and reproducing apparatus of FIG. 38 is set to tequal to a period of a PCM audio signal region and a PCM audio signal ismultiplexed into a vertical blanking period of a recording video signaland then, upon reproduction, a PCM audio signal in such PCM audio signalregion is replaced by a reproduction FM video signal of a precedingfield prior by a period corresponding to the delay time τ before it isFM demodulated, it need not be such specific delay time, but may haveany other delay time. Thus, similar effects can be exhibited if a signalin a PCM audio signal region is replaced by a reproduction FM videosignal other than a signal in such PCM audio signal region.

Further, while such a PCM audio signal mixed with a reproduction FMvideo signal as seen from a waveform (a) of FIG. 41 is processed, uponreproduction, as it is as a reproduction signal in the magneticrecording and reproducing apparatus of FIG. 38, also where the magneticrecording and reproducing apparatus is constructed otherwise such thatan FM video signal and a PCM audio signal of a reproduction signal areseparated as seen from a waveform (b) in FIG. 41 at an output, forexample, of the limiter 32, a reproduction video signal after FMdemodulation will make such a noise in a PCM audio signal region as seenfrom the waveform (c) in FIG. 57 and also from FIG. 54. Accordingly,similarly as in the magnetic recording and reproducing apparatus of FIG.38, the switch 82 is changed over in accordance with a PCM region signaloutputted from the PCM region signal generator 80 to select, in a videosignal region, such reproduction FM video signal (waveform (b) in FIG.41), but select, in a PCM audio signal region, a signal (waveform (c) inFIG. 41) obtained by delaying the reproduction FM video signal by thedelay time T by means of the delay element 81. With such alternativeconstruction, similar effects to those of the magnetic recording andreproducing apparatus of FIG. 38 can be attained.

Further, while the PCM region signal generator 80 of the magneticrecording and reproducing apparatus of FIG. 38 generates a PCM regionsignal by such construction that it detects an end timing of a PCM audiosignal region in a reproduction signal and predicts a starting time of anext PCM audio signal region from a result of such detection, a PCMregion signal may be generated in any other manner or by any othermeans. For example, a PCM region signal may be generated in accordancewith a timing of a head changing over signal.

Further, while a PCM audio signal is inserted into a vertical blankingperiod of an FM modulated video signal in accordance with a suitablechange over operation of the switches 13 and 14 in the magneticrecording and reproducing apparatus of FIG. 38, it may be inserted insome other way into an FM modulated video signal. For example, a PCMaudio signal may be inserted in several separate parts into a horizontalblanking period of an FM modulated video signal. Further, also in thecase wherein a PCM audio signal for one field is inserted in severalparts into a segment blanking period and a vertical blanking period ofan FM modulated video signal and recorded onto and then reproduced froma magnetic tape in a video tape recorder of the type wherein a videosignal for one field is separated into a plurality of segments (a casewherein a video signal is separated into two segments is illustrated inFIG. 58) and recorded onto and reproduced from a magnetic tape, if suchconstruction is employed that a region of a PCM audio signal mixed witha reproduction FM video signal in a reproduction signal is identifiedupon reproduction to generate a controlling signal representative ofsuch PCM audio signal region and the switch circuit 82 is changed overin accordance with such controlling signal, then similar effects can beexhibited with such a recording format wherein a PCM audio signal isrecorded in a segment blanking period.

Further, while the magnetic recording and reproducing apparatus of FIG.38 is constructed such that a magnetic tape is wound over an angle of180 degrees on an outer periphery of a rotary drum and a recordingsignal is recorded in one track for one field onto the magnetic tape,the winding angle and the recording format are not limited such specificones. For example, a signal for one field may otherwise be recorded in aplurality of tracks as in a multi-channel multi-segment recordingsystem.

While the magnetic recording and reproducing apparatus shown in FIG. 38and described above is in the form of a video tape recorder wherein anFM video signal is recorded onto and reproduced from a magnetic tape bymeans of a rotary head, it may have any other form only if an FMmodulated video signal is recorded and/or reproduced in a time divisionmultiplexed condition with a digital audio signal. For example, themagnetic recording and reproducing apparatus may be a video signalrecording and reproducing apparatus such as a laser disk (LD) apparatusor an opto-magnetic disk apparatus or may be such a video signalrecording and reproducing apparatus wherein a video signal is FMmodulated and recorded onto and reproduced from a record medium in theform of a disk as shown in FIG. 42. Referring to FIG. 42, the magneticrecording and reproducing apparatus shown is substantially similar inconstruction to the magnetic recording and reproducing apparatus of FIG.38 except that a recording signal outputted from the recording amplifier16 is recorded, upon recording when a switch 96 is closed to therecording system (REC) side, onto a disk-shaped record medium 98 bymeans of a recording/reproducing head 97, and the thus recorded signalis reproduced, upon reproduction when the switch 96 is closed to thereproducing system (PB) side, from the disk-shaped record medium 98 bythe recording/reproducing head 97. Also with the magnetic recording andreproducing apparatus of FIG. 42, similar effects to those of themagnetic recording and reproducing apparatus of FIG. 38 can be attained.

Referring now to FIG. 43, there is shown another modification to themagnetic recording and reproducing apparatus shown in FIG. 38. Thepresent magnetic recording and reproducing apparatus is modified suchthat it includes a delay element 83 having a delay time equal to ahorizontal scanning period (1 H) of a video signal in place of the delayelement 81 the delay time of which is t equal to a period of a PCM audiosignal region such that a signal in a PCM audio signal region isreplaced, due to a suitable switching operation of the switch circuit82, by a reproduction FM video signal including a repetition of data ofa last line of a preceding field to a blanking period in which a PCMaudio signal.

In particular, the switch circuit 82 is changed over, in accordance witha PCM region signal from the PCM region signal generator 80 in the PCMdecoder 79, to select and transmit, in a video signal region, areproduction FM video signal outputted from the limiter 32 to the FMdemodulator 21 as it is, but select, in a PCM audio signal region, anoutput of the delay element 83 having a delay time equal to a horizontalscanning period 1 H. Since a reproduction FM video signal which is dataof a last line of a preceding field to the PCM audio signal region isoutputted repetitively from the delay element 83, a signal in a PCMaudio signal region of a reproduction signal outputted from the switchcircuit 82 is a signal including a repetition of a reproduction FM videosignal which is data of a last line of a preceding field. Then, anoutput of the switch circuit 82 is FM demodulated by the FM demodulator21, and high frequency components thereof emphasized by the pre-emphasiscircuit 10 in the recording system are de-emphasized by the de-emphasiscircuit 22. Consequently, a reproduction video signal wherein highfrequency noises are reduced is obtained. In the reproduction videosignal thus obtained, a signal in a PCM audio signal region is replacedrepetitively by a reproduction video signal of a last line of apreceding field. Accordingly, synchronizing separation of a reproductionvideo signal can be performed accurately, and the clamp circuit 24 canoperate normally. Further, a synchronizing signal is added also to asignal in a PCM audio signal region. Consequently, a signal in a PCMaudio signal region can be clamped, and sags can be reduced.

It is to be noted that, while the delay time of the delay element 83 ofthe magnetic recording and reproducing apparatus of FIG. 43 is set to 1H, that is, a horizontal scanning period of a video signal and a PCMaudio signal is multiplexed into a vertical blanking period of arecording video signal and then, upon reproduction, a PCM audio signalin such PCM audio signal region is repetitively replaced by areproduction FM video signal of a last line of a preceding field beforeit is FM demodulated, it need not be such specific delay time, but maybe equal to or longer than two horizontal scanning periods 2 H. Thus,similar effects can be exhibited if a signal in a PCM audio signalregion is replaced repetitively by a reproduction FM video signal otherthan a signal in such PCM audio signal region.

Further, while such a PCM audio signal mixed with a reproduction FMvideo signal as seen from the waveform (a) of FIG. 41 is processed, uponreproduction, as it is as a reproduction signal in the modified magneticrecording and reproducing apparatus of FIG. 43, also where the magneticrecording and reproducing apparatus is constructed otherwise such thatan FM video signal and a PCM audio signal of a reproduction signal areseparated as seen from the waveform (b) in FIG. 41 at an output, forexample, of the limiter 32, a reproduction video signal after FMdemodulation will make such a noise in a PCM audio signal region as seenfrom the waveform (c) in FIG. 57 and also from FIG. 54. Accordingly,similarly as in the magnetic recording and reproducing apparatus of FIG.38, the switch 82 is changed over in accordance with a PCM region signaloutputted from the PCM region signal generator 80 to select, in a videosignal region, such reproduction FM video signal, but select, in a PCMaudio signal region, a signal obtained by delaying the reproduction FMvideo signal by the delay time 1 H by means of the delay element 81.With such alternative construction, similar effects to those of themagnetic recording and reproducing apparatus of FIG. 38 can be attained.

Further, while the PCM region signal generator 80 of the magneticrecording and reproducing apparatus of FIG. 38 generates a PCM regionsignal by such construction that it detects an end timing of a PCM audiosignal region in a reproduction signal and predicts a starting time of anext PCM audio signal region from a result of such detection, a PCMregion signal may be generated in any other manner or by any othermeans. For example, a PCM region signal may be generated in accordancewith a timing of a head change over signal.

Further, while a PCM audio signal is inserted into a vertical blankingperiod of an FM video signal in accordance with a suitable changing overoperation of the switches 13 and 14 in the magnetic recording andreproducing apparatus of FIG. 43, it may be inserted in some other wayinto an FM modulated video signal. For example, a PCM audio signal maybe inserted in several separate parts into a horizontal blanking periodof an FM modulated video signal. Further, also in the case wherein a PCMaudio signal for one field is inserted in several parts into a segmentblanking period and a vertical blanking period of an FM modulated videosignal and recorded onto and then reproduced from a magnetic tape in avideo tape recorder of the type wherein a video signal for one field isseparated into a plurality of segments (a case wherein a video signal isseparated into two segments is illustrated in FIG. 58) and recorded ontoand reproduced from a magnetic tape, if such construction is employedthat a region of a PCM audio signal mixed with a reproduction FM videosignal in a reproduction signal is identified upon reproduction togenerate a controlling signal representative of such PCM audio signalregion and the switch circuit 82 is changed over in accordance with suchcontrolling signal, then similar effects can be exhibited with such arecording format wherein a PCM audio signal is recorded in a segmentblanking period.

Further, while the magnetic recording and reproducing apparatus of FIG.43 is constructed such that a magnetic tape is wound over an angle of180 degrees on an outer periphery of a rotary drum and a recordingsignal is recorded in one track for one field onto the magnetic tape,the winding angle and the recording format are not limited such specificones. For example, a signal for one field may otherwise be recorded in aplurality of tracks as in a multi-channel multi-segment recordingsystem.

While the magnetic recording and reproducing apparatus shown in FIG. 43and described above is in the form of a video tape recorder wherein anFM video signal is recorded onto and reproduced from a magnetic tape bymeans of a rotary head, it may have any other form only if a digitalaudio signal is recorded and/or reproduced in a time divisionmultiplexed condition with an FM modulated video signal. For example,the magnetic recording and reproducing apparatus may be a video signalrecording and reproducing apparatus such as a laser disk (LD) apparatusor an opto-magnetic disk apparatus or may be such a video signalrecording and reproducing apparatus wherein a video signal is FMmodulated and recorded onto and reproduced from a record medium in theform of a disk as shown in FIG. 44. Referring to FIG. 44, the magneticrecording and reproducing apparatus shown is substantially similar inconstruction to the magnetic recording and reproducing apparatus of FIG.43 except that a recording signal outputted from the recording amplifier16 is recorded, upon recording when a switch 96 is closed to therecording system (REC) side, onto a disk-shaped record medium 98 bymeans of a recording/reproducing head 97, and the thus recorded signalis reproduced, upon reproduction when the switch 96 is closed to thereproducing system (PB) side, from the disk-shaped record medium 98 bythe recording/reproducing head 97, similarly as in the magneticrecording and reproducing apparatus shown in FIG. 42. Also with themagnetic recording and reproducing apparatus of FIG. 44, similar effectsto those of the magnetic recording and reproducing apparatus of FIG. 43can be attained.

Referring now to FIG. 45, there is shown a further modification to themagnetic recording and reproducing apparatus of FIG. 38. The presentmagnetic recording and reproducing apparatus is modified such that itincludes a PCM decoder 85 including a PCM region signal generator 86therein, an FM signal generator 87 and a switch 88 in place of the PCMdecoder 79 including the PCM region signal generator 80 therein, thedelay element 81 and the switch 82, respectively.

The PCM decoder 85 detects a PCM audio signal for one field periodinserted in a vertical blanking period of a reproduction signaltransmitted thereto from the head change over circuit 30 and performssuch processing as error correction, de-shuffling and error modificationto restore an original audio signal. The PCM audio signal generator 86in the PCM decoder 85 identifies a PCM audio signal region of areproduction signal and generates a PCM region signal representative ofsuch PCM audio signal region in such a manner as described hereinabove.The FM signal generator 87 generates an FM signal including a carrierhaving a frequency fc, which is to make, after FM demodulation thereof,a signal overlapped with a gray level and having a fixed frequency fPand an amplitude B. The switch circuit 88 is changed over in response toa PCM region signal outputted from the PCM region signal generator 86 toselect one of a reproduction signal outputted from the limiter 32 and anoutput of the FM signal generator 87.

In operation, the recording system of the magnetic recording andreproducing apparatus of FIG. 45 operates, upon recording, in a similarmanner to the recording system of the magnetic recording and reproducingapparatus of FIG. 38.

On the other hand, upon reproduction, the rotary heads 29a and 29b,reproduction amplifiers 19a and 19b and head change over circuit 30 ofthe reproducing system of the magnetic recording and reproducingapparatus of FIG. 45 operate in a similar manner to those of thereproducing system of the magnetic recording and reproducing apparatusof FIG. 38. Thus, such a single reproduction signal as seen from thewaveform (c) of FIG. 62 is outputted from the head change over circuit30. The reproduction signal is transmitted to the reproduction equalizer20 and also to the PCM decoder 85. The PCM decoder 85 detects a PCMaudio signal for one field period inserted in a vertical blanking periodof the reproduction signal and performs such processing as errorcorrection, de-shuffling and error modification to restore and output anoriginal audio signal therefrom. Meanwhile, the reproduction equalizer20 compensates for a frequency characteristic of a reproduction FM videosignal of the received reproduction signal, and an output of thereproduction equalizer 20 is transmitted to the limiter 32, at whichamplitude variation components of the reproduction FM video signal areremoved.

By the way, if a PCM audio signal multiplexed in a vertical blankingperiod with a reproduction FM video signal is FM demodulated as it is bythe FM demodulator 21, then a reproduction video signal outputted fromthe FM demodulator 21 in a PCM audio signal region will present such anoutput signal waveform as shown by the waveform (a) in FIG. 39 as if itincludes noise.

Thus, the FM signal generator 87 generates an FM demodulation signal,for example, having a carrier frequency fC which is to make, after FMdemodulation thereof, a signal overlapped with a gray level and having afixed frequency fP and an amplitude B, and an output of the FM signalgenerator 87 and a reproduction signal outputted from the limiter 32 areinputted to the switch circuit 88, which is changed over in accordancewith a PCM region signal representative of a PCM audio signal region andgenerated in such a manner as described hereinabove from the PCM regionsignal generator 86 in the PCM decoder 85, so as to obtain a signal fromwhich such a reproduction video signal having a waveform as shown inFIG. 17 can be produced by FM demodulation thereof.

In particular, the switch circuit 88 is changed over, in accordance witha pulse representative of a PCM audio signal region and a video signalregion and received from the PCM region signal generator 86 in the PCMdecoder 85, to select and transmit, in a period of a video signalregion, a reproduction signal (waveform (a) in FIG. 46) outputted fromthe limiter 32, but select, in a period of a PCM audio signal region, anoutput (waveform (b) in FIG. 46) of the FM signal generator 87.Consequently, an output of the switch circuit 88 presents such awaveform (c) as shown in FIG. 46. Accordingly, if the output of theswitch circuit 88 is transmitted to and FM demodulated by the FMdemodulator 21 and passed through the de-emphasis circuit 22, a signalin a PCM audio signal region of an output reproduction video signal ofthe de-emphasis circuit 22 presents such a waveform as shown in FIG. 17wherein a signal of a frequency fP and an amplitude B is overlapped witha gray level.

Where such construction is employed, a signal in a PCM audio signalregion of an FM demodulated reproduction video signal can be formed as asignal overlapped with a gray level and having the fixed frequency fPand the amplitude B, and consequently, synchronization separation of areproduction video signal can be performed accurately. Further, since asignal selected in a PCM audio signal region does not include only a dclevel signal, sags can be reduced.

A reproduction signal outputted from the switch circuit 88 issubsequently supplied to the FM demodulator 21. Consequently, thereproduction signal is thereafter processed successively by the FMdemodulator 21, de-emphasis circuit 22, clamp circuit 24, A/D converter25, second synchronizing separator circuit 26, reproduction signalprocessing circuit 27 and D/A converter 28 in a similar manner as in themagnetic recording and reproducing apparatus of FIG. 43. Consequently, agroove reproduction video signal can be obtained.

It is to be noted that, while the FM signal generator 87 of the magneticrecording and reproducing apparatus of FIG. 45 generates and outputs anFM signal which has a carrier frequency f_(c) and is to make a signalhaving a fixed frequency f_(p) and an amplitude B and overlapped with agray level after FM demodulation thereof, it need not generate suchspecific FM signal, but similar effects can be obtained by any otherconstruction if it generates an FM modulating signal different from afixed dc current level signal and having such a frequency at which sagscan be reduced between a pedestal level and a white level after FMdemodulation thereof.

Further, while the PCM region signal generator 86 of the magneticrecording and reproducing apparatus of FIG. 45 generates a PCM regionsignal by such construction that it detects an end timing of a PCM audiosignal region in a reproduction signal and predicts a starting time of anext PCM audio signal region from a result of such detection, a PCMregion signal may be generated in any other manner or by any othermeans. For example, a PCM region signal may be generated in accordancewith a timing of a head change over signal.

Further, while a PCM audio signal mixed with a reproduction FM videosignal is processed, upon reproduction, as it is as a reproductionsignal in the modified magnetic recording and reproducing apparatus ofFIG. 45, also where the magnetic recording and reproducing apparatus isconstructed otherwise such that an FM video signal and a PCM audiosignal of a reproduction signal are separated as seen from a waveform(b) in FIG. 47 at an output, for example, of the limiter 32, areproduction video signal after FM demodulation will make such a noisein a PCM audio signal region as seen from the waveform (c) in FIG. 57and also from FIG. 54. Accordingly, similarly as in the magneticrecording and reproducing apparatus of FIG. 38, the switch 88 is changedover in accordance with a PCM region signal outputted from the PCMregion signal generator 86 to select, in a video signal region, suchreproduction FM video signal (waveform (b) in FIG. 47), but select, in aPCM audio signal region, an output (waveform (c) in FIG. 47) of the FMsignal generator 87. With such alternative construction, similar effectsto those of the magnetic recording and reproducing apparatus of FIG. 38can be attained.

Further, while a PCM audio signal is inserted into a vertical blankingperiod of an FM video signal in accordance with a suitable change overoperation of the switches 13 and 14 in the magnetic recording andreproducing apparatus of FIG. 45, it may be inserted in some other wayinto an FM modulated video signal. For example, a PCM audio signal maybe inserted in several separate parts into a horizontal blanking periodof an FM modulated video signal. Further, also in the case wherein a PCMaudio signal for one field is inserted in several parts into a segmentblanking period and a vertical blanking period of an FM modulated videosignal and recorded onto and then reproduced from a magnetic tape in avideo tape recorder of the type wherein a video signal for one field isseparated into a plurality of segments (a case wherein a video signal isseparated into two segments is illustrated in FIG. 58) and recorded ontoand reproduced from a magnetic tape, if such construction is employedthat a region of a PCM audio signal mixed with a reproduction FM videosignal in a reproduction signal is identified upon reproduction togenerate a controlling signal representative of such PCM audio signalregion and the switch circuit 88 is changed over in accordance with suchcontrol signal, similar effects can be exhibited with such a recordingformat wherein a PCM audio signal is recorded in a segment blankingperiod.

Further, while the magnetic recording and reproducing apparatus of FIG.45 is constructed such that a magnetic tape is wound over an angle of180 degrees on an outer periphery of a rotary drum and a recordingsignal is recorded in one track for one field onto the magnetic tape,the winding angle and the recording format are not limited such specificones. For example, a signal for one field may otherwise be recorded in aplurality of tracks as in a multi-channel multi-segment recordingsystem.

While the magnetic recording and reproducing apparatus shown in FIG. 45is in the form of a video tape recorder wherein an FM video signal isrecorded onto and reproduced from a magnetic tape by means of a rotaryhead, it may have any other form only if a digital audio signal isrecorded and/or reproduced in a time division multiplexed condition withan FM modulated video signal. For example, the magnetic recording andreproducing apparatus may be a video signal recording and reproducingapparatus such as a laser disk (LD) apparatus or an opto-magnetic diskapparatus or may be such a video signal recording and reproducingapparatus wherein a video signal is FM modulated and recorded onto andreproduced from a record medium in the form of a disk as shown in FIG.48. Referring to FIG. 48, the magnetic recording and reproducingapparatus shown is substantially similar in construction to the magneticrecording and reproducing apparatus of FIG. 45 except that a recordingsignal outputted from the recording amplifier 16 is recorded, uponrecording when a switch 96 is closed to the recording system (REC) side,onto a disk-shaped record medium 98 by means of a recording/reproducinghead 97, and the thus recorded signal is reproduced, upon reproductionwhen the switch 96 is closed to the reproducing system (PB) side, fromthe disk-shaped record medium 98 by the recording/reproducing head 97,similarly as in the magnetic recording and reproducing apparatus shownin FIG. 42 and 44. Also with the magnetic recording and reproducingapparatus of FIG. 48, similar effects to those of the magnetic recordingand reproducing apparatus of FIG. 43 can be attained.

Referring now to FIG. 49, there is shown a yet further modification tothe magnetic recording and reproducing apparatus of FIG. 38. The presentmagnetic recording and reproducing apparatus is modified such that itincludes a PCM decoder 93 including a PCM region signal generator 94therein in place of the PCM decoder 79 including the PCM region signalgenerator 80 and further includes a pair of delay elements I 89 and II90 and a pair of switches 91 and 92 in place of the delay element 81 andthe switch 82, respectively. In particular, the PCM decoder 93 detects aPCM audio signal for one field period inserted in a vertical blankingperiod of a reproduction signal transmitted thereto from the rotary head19a or 19b and performs such processing as error correction,de-shuffling and error modification to restore an original audio signal.The PCM audio signal generator 94 in the PCM decoder 93 accuratelyidentifies a PCM audio signal region of a reproduction signal andgenerates a PCM region signal representative of such PCM audio signalregion in such a manner as described hereinabove. The delay element I 89delays a reproduction signal received from the reproduction amplifier19a by a delay time τ while the other delay element II 90 delays areproduction signal received from the other reproduction amplifier 19bby the same delay time τ. The switches 91 and 92 are changed over inaccordance with a PCM region signal outputted from the PCM region signalgenerator 93.

In operation, the recording system of the magnetic recording andreproducing apparatus of FIG. 49 operates, upon recording, in a similarmanner to the recording system of the magnetic recording and reproducingapparatus of FIG. 38.

On the other hand, upon reproduction, the rotary heads 29a and 29b andreproduction amplifiers 19a and 19b of the reproducing system of themagnetic recording and reproducing apparatus of FIG. 49 operate in asimilar manner to those of the reproducing system of the magneticrecording and reproducing apparatus of FIG. 38. Thus, reproductionsignals amplified by the reproduction amplifiers 19a and 19b aretransmitted to the switch circuits 91 and 92 and delay elements 89 and90, respectively, and also transmitted to the PCM decoder 93. The PCMdecoder 93 detects a PCM audio signal for one field inserted in avertical blanking period of a reproduction signal transmitted theretofrom the reproduction amplifier 19a or 19b and performs de-shuffling,error modification and so forth to restore an original audio signal. Thethus restored original audio signal is outputted from the PCM decoder 93as an output reproduction audio signal of the reproducing system of themagnetic recording and reproducing apparatus.

By the way, if a PCM audio signal multiplexed in a vertical blankingperiod with a reproduction FM video signal is FM demodulated as it is bythe FM demodulator 21, a reproduction video signal outputted from the FMdemodulator 21 in a PCM audio signal region will present such an outputsignal waveform as shown by the waveform (a) in FIG. 39 as if itincludes noises.

Thus, a reproduction signal outputted from the reproduction amplifier19a and having such a waveform (a) as shown in FIG. 50 is inputted tothe switch circuit 91 and the delay circuit I 89 while anotherreproduction signal outputted from the reproduction amplifier 19b andhaving such a waveform (b) as shown in FIG. 50 is inputted to the switchcircuit 92 and the delay element II 90. Then, the switch circuits 91 and92 are changed over so that a signal in a PCM audio signal region of areproduction video signal after FM demodulation may be replaced by asignal of a line preceding by a period equal to a period of a PCM audiosignal region of a preceding field as seen from the waveform (b) in FIG.39. A PCM region signal generated in such a manner as describedhereinabove by the PCM region signal generator 94 in the PCM decoder 93is transmitted to the switches 91 and 92.

The switch 91 thus selects, in a video signal region, a reproductionsignal (waveform (a) in FIG. 50) of the rotary head 29a outputted fromthe reproduction amplifier 19a, but selects, in a PCM audio signalregion, another reproduction signal (waveform (b) in FIG. 50) of theother rotary head 29b outputted from the reproduction amplifier 19b sothat an output of the delay element II 90 delayed by the time τ may beselected as seen from a waveform (d) in FIG. 50. On the other hand, theswitch circuit 92 selects, in a video signal region, a reproductionsignal (waveform. (b) in FIG. 50) of the rotary head 29b outputted fromthe reproduction amplifier 19b, but selects, in a PCM audio signalregion, a reproduction signal (waveform (a) in FIG. 50) of the rotaryhead 29a outputted from the reproduction amplifier 19a so that an outputof the delay element I 89 delayed by the time τ may be selected. Thus,from the delay element I 89, a reproduction FM video signal is outputtedwhich is produced by delaying a signal of a preceding field to a PCMaudio signal region of a reproduction signal from the reproductionamplifier 19a by the delay time τ . On the other hand, from the otherdelay element II 90, another reproduction FM video signal is outputtedwhich is produced by delaying a signal of a preceding field to a PCMaudio signal region of a reproduction signal of the reproductionamplifier 19b by the delay time τ. Consequently, an output of the switchcircuit 91 presents such a waveform (e) as shown in FIG. 50 while anoutput of the other switch circuit 92 presents such a waveform (f) asshown in FIG. 50. Accordingly, a signal in a PCM audio signal region ofa reproduction signal from each of the rotary heads 29a and 29b is areproduction FM video signal for a period of the delay time τ of apreceding field to the PCM audio signal region.

Outputs of the switch circuits 91 and 92 are inputted to the head changeover circuit 30, which is changed over in response to a head change oversignal so as to select a reproduction signal from one of the rotaryheads 29a and 29b which contacts with the magnetic tape 200 to make asingle reproduction signal. Such reproduction signal outputted from thehead changing over circuit 30 presents such a waveform (g) as shown inFIG. 50. The reproduction signal outputted from the head changing overcircuit 30 is transmitted to the reproduction equalizer 20, at which afrequency characteristic of a reproduction FM video signal thereof iscompensated for. Then, an output reproduction signal of the reproductionequalizer 20 is inputted to the limiter 32, at which amplitude variationcomponents of the reproduction FM video signal are removed. An output ofthe limiter 32 is then supplied to and FM demodulated by the FMdemodulator 21, and then it is supplied to the de-emphasis circuit 22,at which high frequency components emphasized by the pre-emphasiscircuit 10 in the recording system are de-emphasized. Consequently, sucha reproduction video signal in which high frequency noises have beenreduced as shown by the waveform (b) in FIG. 39 is obtained. Thus, sincea signal in a PCM audio signal region is replaced by a reproductionvideo signal of a preceding field, synchronizing separation of areproduction video signal can be performed accurately and the clampcircuit 24 at a next stage operates normally. Further, since asynchronizing signal is added also to a signal in a PCM audio signalregion, a signal can be clamped also in a PCM audio signal region, andthe sags are reduced.

A reproduction signal outputted from the de-emphasis circuit 22 issubsequently supplied to the clamp circuit 24, and consequently, thereproduction signal is thereafter processed successively by the clampcircuit 24, A/D converter 25, second synchronizing separator circuit 26,reproduction signal processing circuit 27 and D/A converter 28 in asimilar manner as in the magnetic recording and reproducing apparatus ofFIG. 43. Consequently, a groove reproduction video signal can beobtained.

It is to be noted that, while the delay time of the delay elements 89and 90 of the magnetic recording and reproducing apparatus of FIG. 49 isset to t equal to a period of a PCM audio signal region and a PCM audiosignal in such PCM audio signal region is replaced by a reproduction FMvideo signal of a preceding field prior by a period corresponding to thedelay time τ, it need not be such specific delay time, but may have anyother delay time. Thus, similar effects can be exhibited if a signal ina PCM audio signal region is replaced by a reproduction FM video signalother than a signal in such PCM audio signal region.

Further, while the PCM region signal generator 84 of the magneticrecording and reproducing apparatus of FIG. 45 generates a PCM regionsignal by such construction that it detects an end timing of a PCM audiosignal region in a reproduction signal and predicts a starting time of anext PCM audio signal region from a result of such detection, a PCMregion signal may be generated in any other manner or by any othermeans. For example, a PCM region signal may be generated in accordancewith a timing of a head changing over signal.

Further, while a reproduction FM video signal and a PCM audio signalmixed with such reproduction FM video signal are processed, uponreproduction, as they are as reproduction signals by a suitable changeover operation of the switch circuits 91 and 92 of the magneticrecording and reproducing apparatus of FIG. 49, similar effects can beattained also where the reproducing system is constructed otherwise suchthat, for example, each of the reproduction amplifiers provides such apair of separate reproduction signals including an FM video signal and aPCM audio signal as seen from waveforms (c) and (d) of FIG. 51 and suchFM video signals and PCM audio signals are inputted to the switchcircuits and the delay elements while the switch circuits are changedover in accordance with a PCM region signal, whereupon an output of thehead change over circuit presents such a waveform (g) as shown in FIG.51.

Further, while a PCM audio signal is inserted into a vertical blankingperiod of an FM video signal in accordance with a suitable change overoperation of the switches 13 and 14 in the magnetic recording andreproducing apparatus of FIG. 49, it may be inserted in some other wayinto an FM modulated video signal. For example, a PCM audio signal maybe inserted in several separate parts into a horizontal blanking periodof an FM modulated video signal. Further, also in the case wherein a PCMaudio signal for one field is inserted in several parts into a segmentblanking period and a vertical blanking period of an FM modulated videosignal and recorded onto and then reproduced from a magnetic tape in avideo tape recorder of the type wherein a video signal for one field isseparated into a plurality of segments (a case wherein a video signal isseparated into two segments is illustrated in FIG. 58) and recorded ontoand reproduced from a magnetic tape, if such construction is employedthat a region of a PCM audio signal mixed with a reproduction FM videosignal in a reproduction signal is identified upon reproduction togenerate a controlling signal representative of such PCM audio signalregion and the switch circuits 91 and 92 are changed over in accordancewith such controlling signal, similar effects can be exhibited with sucha recording format wherein a PCM audio signal is recorded in a segmentblanking period.

Further, while the magnetic recording and reproducing apparatus of FIG.49 is constructed such that a magnetic tape is wound over an angle of180 degrees on an outer periphery of a rotary drum and a recordingsignal is recorded in one track for one field onto the magnetic tape,the winding angle and the recording format are not limited such specificones. For example, a signal for one field may otherwise be recorded in aplurality of tracks as in a multi-channel multi-segment recordingsystem.

Having now fully described the invention, it will be apparent to one ofordinary skill in the art that many changes and modifications can bemade thereto without departing from the spirit and scope of theinvention as set forth herein.

What is claimed is:
 1. A magnetic recording and reproducing apparatus ofthe type wherein a video signal is FM modulated and recorded onto andreproduced from a magnetic medium by a rotary head, comprising:changeover switch means for selectively inserting, upon recording, a PCMmodulated audio signal into a blanking period of a FM modulated videosignal; a PCM region signal generator for identifying a region of a PCMmodulated audio signal in a reproduction signal reproduced by the rotaryhead and for generating a control signal representative of a PCM audiosignal region; FM demodulating means for FM demodulating a reproductionsignal from the rotary head into a reproduction FM demodulation signal;and a clip circuit for clipping a lower end portion of a PCM audiosignal region of a reproduction FM demodulation signal from said FMdemodulating means in accordance with a control signal generated fromsaid PCM region signal generator.
 2. A magnetic recording andreproducing apparatus of the type wherein a video signal is FM modulatedan a digital audio signal is time division multiplexed into a blankingperiod of the FM modulated video signal and recorded onto and reproducedfrom a magnetic record medium by a rotary head, comprising:region signalgenerating means for identifying a region of a digital audio signal in areproduction signal reproduced by the rotary head and for generating acontrol signal representative of a region of a digital audio signal; FMdemodulating means for FM demodulating a reproduction signal from therotary head; and a clip circuit for clipping an upper end portion and alower end portion in a digital audio signal region of an FM demodulationsignal from said FM demodulator in accordance with an output signal ofsaid region signal generating means.
 3. A magnetic recording andreproducing apparatus as claimed in claim 2, wherein said clip circuitincludes a white clip circuit for clipping an upper end portion in adigital audio signal region of an FM demodulation signal from said FMmodulator which is higher than a white level of such FM demodulationsignal in accordance with an output signal of said region signalgenerating means.
 4. A magnetic recording and reproducing apparatus asclaimed in claim 2, wherein said clip circuit includes a pedestal clipcircuit for clipping a lower end portion in a digital audio signalregion of an FM demodulation signal from said FM modulator which islower than a pedestal level of such FM demodulation signal in accordancewith an output signal of said region signal generating means.
 5. Arecording and reproducing apparatus wherein a reproduced signal,recorded on a recording medium, has an audio signal which has beeninserted into a blanking period of a FM modulated video signal,comprising:a FM demodulator; identifying means for identifying a regionin the reproduced signal which has the inserted audio signal and forproducing a first signal in response thereof; and compensating means, inresponse to said first signal, for removing the inserted audio signalfrom the reproduced signal, thereby eliminating any effectualcharacteristics of noise that the audio signal has on the demodulationprocess of said FM demodulator.
 6. The apparatus as claimed in claim 5wherein said compensating means comprises a clipping circuit to clip theinserted audio signal from a demodulated video signal in response tosaid first signal.
 7. The magnetic recording and reproducing apparatusas claimed in claim 6, wherein said clip circuit includes a white clipcircuit for clipping an upper end portion in the audio signal region ofan FM demodulation signal from said FM demodulator which is higher thana white level of such FM demodulation signal in accordance with anoutput signal of said identifying means.
 8. The magnetic recording andreproducing apparatus as claimed in claim 6, wherein said clip circuitincludes a pedestal clip circuit for clipping a lower end portion in theaudio signal region of an FM demodulation signal from said FMdemodulator which is lower than a pedestal level of such FM demodulationsignal in accordance with an output signal of said identifying means. 9.The apparatus as claimed in claim 5 wherein said compensating meanscomprises:a level signal generator to output a second signal having acertain level; and switching means for selecting said second signal inresponse to said first signal and for selecting an output of said FMdemodulator in response to an absence of said first signal.
 10. Theapparatus as claimed in claim 5 wherein said compensating meanscomprises:a de-emphasis circuit to de-emphasize high frequencies in theFM demodulated signal outputted from said FM demodulator; a level signalgenerator to output a second signal having a certain level; andswitching means for selecting said second signal in response to saidfirst signal and for selecting an output of said de-emphasis circuit inresponse to an absence of said first signal.
 11. The apparatus asclaimed in claim 5 wherein said compensating means comprises:a levelsignal generator to output a second signal having a certain frequency;and switching means for selecting said second signal in response to saidfirst signal and for selecting the reproduced signal in response to anabsence of said first signal, said selected signal being inputted tosaid FM demodulator.
 12. The apparatus as claimed in claim 5 whereinsaid compensating means comprises:delay means for delaying an FMdemodulated signal from said FM demodulator; and switching means forselecting the delayed signal in response to said first signal and forselecting an output of said FM demodulator in response to an absence ofsaid first signal.
 13. The apparatus as claimed in claim 12 wherein saiddelay is equal to one horizontal scanning period.
 14. The apparatus asclaimed in claim 5 wherein said compensating means comprises:a blankingdata generator to output a second signal representing blanking data; andswitching means for selecting said second signal in response to saidfirst signal and for selecting an output of said FM demodulator inresponse to an absence of said first signal.
 15. The apparatus asclaimed in claim 5 wherein said compensating means comprises:a blankingdata generator to output a second signal representing blanking data,said second signal being frequency modulated; and switching means forselecting said frequency modulated second signal in response to saidfirst signal and for selecting the reproduced signal in response to anabsence of said first signal, said selected signal being fed into saidFM demodulator.
 16. The apparatus as claimed in claim 5 wherein saidcompensating means comprises:an analog/digital converter to convert thereproduced signal to a digital signal; a memory to store said digitalsignal; reading means for reading out contents of said memory and forpreventing the reading out of contents representing the inserted audiosignal in response to said first signal; and a digital/analog converterto convert the read signal to an analog signal.
 17. The apparatus asclaimed in claim 5 wherein said compensating means comprises:a memory tostore the reproduced signal; and reading means for reading out contentsof said memory and for preventing the reading out of contentsrepresenting the inserted audio signal in response to said first signal.